See also translations.
This document is also available in these non-normative formats: XML and Change markings relative to previous Working Draft.
Copyright © 2011 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
XML is a versatile markup language, capable of labeling the information content of diverse data sources including structured and semi-structured documents, relational databases, and object repositories. A query language that uses the structure of XML intelligently can express queries across all these kinds of data, whether physically stored in XML or viewed as XML via middleware. This specification describes a query language called XQuery, which is designed to be broadly applicable across many types of XML data sources.
XQuery 3.0 is an extended version of the XQuery 1.0 Recommendation published on 23 January 2007. A list of changes made since XQuery 1.0 can be found in J Change Log. Here are some of the new features in XQuery 3.0:
group by
clause in FLWOR Expressions (3.9.7 Group By Clause).
tumbling window
and sliding window
in
FLWOR Expressions (3.9.4 Window
Clause).
count
clause in FLWOR Expressions (3.9.6 Count Clause).
allowing empty
in 3.9.2 For Clause, for
functionality similar to outer joins in SQL.
try
/catch
expressions (3.14 Try/Catch Expressions).
Dynamic function invocation (3.2.2 Dynamic Function Invocation).
Inline functions (3.1.7 Inline Functions).
Private functions (4.18 Function Declaration).
Switch expressions (3.12 Switch Expression).
Computed namespace constructors (3.8.3.7 Computed Namespace Constructors).
Output declarations (2.2.4 Serialization).
Annotations (4.15 Annotations).
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This is one document in a set of seven documents that are being progressed to Recommendation together (XQuery 3.0, XQueryX 3.0, XSLT 3.0, Data Model 3.0, Functions and Operators 3.0, Serialization 3.0, XPath 3.0).
This is a Working Draft as described in the Process Document. It was developed by the W3C XML Query Working Group, which is part of the XML Activity. The Working Group expects to advance this specification to Recommendation Status.
This public Working Draft makes a number of substantive technical changes (as well as many editorial changes), including new features, adopted since the previous Working Draft was published. Please note that this Working Draft of XQuery 3.0 represents the second version of a previous W3C Recommendation.
No implementation report currently exists. However, a Test Suite for XQuery 3.0 is under development.
This document incorporates changes made against the previous publication of the Working Draft. Changes to this document since the previous publication of the Working Draft are detailed in J Change Log.
Please report errors in this document using W3C's public Bugzilla system (instructions can be found at http://www.w3.org/XML/2005/04/qt-bugzilla). If access to that system is not feasible, you may send your comments to the W3C XSLT/XPath/XQuery public comments mailing list, public-qt-comments@w3.org. It will be very helpful if you include the string “[XQuery30]” in the subject line of your report, whether made in Bugzilla or in email. Please use multiple Bugzilla entries (or, if necessary, multiple email messages) if you have more than one comment to make. Archives of the comments and responses are available at http://lists.w3.org/Archives/Public/public-qt-comments/.
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
1 Introduction
2 Basics
2.1 Expression
Context
2.1.1 Static Context
2.1.2 Dynamic Context
2.2 Processing Model
2.2.1 Data Model Generation
2.2.2 Schema Import Processing
2.2.3 Expression Processing
2.2.3.1
Static Analysis Phase
2.2.3.2
Dynamic Evaluation Phase
2.2.4 Serialization
2.2.5 Consistency Constraints
2.3 Error
Handling
2.3.1 Kinds of Errors
2.3.2 Identifying and Reporting Errors
2.3.3 Handling Dynamic Errors
2.3.4 Errors and Optimization
2.4 Concepts
2.4.1 Document Order
2.4.2 Atomization
2.4.3 Effective Boolean Value
2.4.4 Input Sources
2.4.5 URI Literals
2.4.6 Resolving a Relative URI
2.5 Types
2.5.1 Predefined Schema Types
2.5.2 Namespace-sensitive Types
2.5.3 Typed Value and String Value
2.5.4 SequenceType Syntax
2.5.5 SequenceType Matching
2.5.5.1
Matching a SequenceType and a
Value
2.5.5.2
Matching an ItemType and an
Item
2.5.5.3
Element Test
2.5.5.4
Schema Element Test
2.5.5.5
Attribute Test
2.5.5.6
Schema Attribute Test
2.5.5.7
Function Test
2.5.6 SequenceType Subtype
Relationships
2.5.6.1
The SequenceType Subtype
Judgement
2.5.6.2
The ItemType Subtype
Judgement
2.5.6.3
The Annotation Assertions Subtype
Judgement
2.6 Comments
3 Expressions
3.1 Primary Expressions
3.1.1 Literals
3.1.2 Variable References
3.1.3 Parenthesized Expressions
3.1.4 Context Item Expression
3.1.5 Function Calls
3.1.5.1
Evaluating Function
Calls
3.1.5.2
Function Conversion
Rules
3.1.5.3
Function Item Coercion
3.1.5.4
Evaluating Partial
Function Applications
3.1.6 Literal Function Items
3.1.7 Inline Functions
3.2 Postfix Expressions
3.2.1 Filter Expressions
3.2.2 Dynamic Function
Invocation
3.3 Path
Expressions
3.3.1 Steps
3.3.1.1
Axes
3.3.1.2
Node Tests
3.3.2 Predicates within Steps
3.3.3 Unabbreviated Syntax
3.3.4 Abbreviated Syntax
3.4 Sequence Expressions
3.4.1 Constructing Sequences
3.4.2 Combining Node Sequences
3.5 Arithmetic
Expressions
3.6 Comparison
Expressions
3.6.1 Value Comparisons
3.6.2 General Comparisons
3.6.3 Node Comparisons
3.7 Logical Expressions
3.8 Constructors
3.8.1 Direct Element Constructors
3.8.1.1
Attributes
3.8.1.2
Namespace Declaration Attributes
3.8.1.3
Content
3.8.1.4
Boundary Whitespace
3.8.2 Other Direct Constructors
3.8.3 Computed Constructors
3.8.3.1
Computed Element
Constructors
3.8.3.2
Computed Attribute
Constructors
3.8.3.3
Document Node
Constructors
3.8.3.4
Text Node Constructors
3.8.3.5
Computed Processing Instruction
Constructors
3.8.3.6
Computed Comment
Constructors
3.8.3.7
Computed Namespace
Constructors
3.8.4 In-scope Namespaces of a Constructed
Element
3.9 FLWOR
Expressions
3.9.1 Variable Bindings
3.9.2 For Clause
3.9.3 Let Clause
3.9.4 Window Clause
3.9.4.1
Tumbling Windows
3.9.4.2
Sliding Windows
3.9.4.3
Effects of Window Clauses
on the Tuple Stream
3.9.5 Where Clause
3.9.6 Count Clause
3.9.7 Group By Clause
3.9.8 Order By Clause
3.9.9 Return Clause
3.10 Ordered and Unordered
Expressions
3.11 Conditional
Expressions
3.12 Switch
Expression
3.13 Quantified Expressions
3.14 Try/Catch
Expressions
3.15 Expressions on
SequenceTypes
3.15.1 Instance Of
3.15.2 Typeswitch
3.15.3 Cast
3.15.4 Castable
3.15.5 Constructor Functions
3.15.6 Treat
3.16 Validate
Expressions
3.17 Extension Expressions
4 Modules and Prologs
4.1 Version Declaration
4.2 Module
Declaration
4.3 Boundary-space Declaration
4.4 Default Collation
Declaration
4.5 Base URI
Declaration
4.6 Construction Declaration
4.7 Ordering Mode Declaration
4.8 Empty
Order Declaration
4.9 Copy-Namespaces Declaration
4.10 Decimal-Format Declaration
4.11 Schema
Import
4.12 Module
Import
4.12.1 Module URIs
4.12.2 Multiple Modules with the same
Module URI
4.12.3 Location URIs
4.12.4 Cycles
4.13 Namespace Declaration
4.14 Default Namespace Declaration
4.15 Annotations
4.16 Variable Declaration
4.17 Context Item Declaration
4.18 Function
Declaration
4.19 Option Declaration
5 Conformance
5.1 Minimal Conformance
5.2 Optional Features
5.2.1 Schema Import Feature
5.2.2 Schema Validation Feature
5.2.3 Static Typing Feature
5.2.4 Module Feature
5.2.5 Serialization Feature
5.3 Data Model Conformance
5.4 Syntax
Extensions
A XQuery 3.0 Grammar
A.1 EBNF
A.1.1 Notation
A.1.2 Extra-grammatical
Constraints
A.1.3 Grammar Notes
A.2 Lexical
structure
A.2.1 Terminal Symbols
A.2.2 Terminal Delimitation
A.2.3 End-of-Line Handling
A.2.3.1
XML 1.0 End-of-Line
Handling
A.2.3.2
XML 1.1 End-of-Line
Handling
A.2.4 Whitespace Rules
A.2.4.1
Default Whitespace
Handling
A.2.4.2
Explicit Whitespace
Handling
A.3 Reserved Function Names
A.4 Precedence Order (Non-Normative)
B Type Promotion
and Operator Mapping
B.1 Type
Promotion
B.2 Operator
Mapping
C Context Components
C.1 Static Context
Components
C.2 Dynamic Context
Components
D Implementation-Defined
Items
E References
E.1 Normative References
E.2 Non-normative References
E.3 Background Material
F Error Conditions
G The application/xquery Media
Type
G.1 Introduction
G.2 Registration of MIME Media Type
application/xquery
G.2.1 Interoperability
Considerations
G.2.2 Applications Using this Media
Type
G.2.3 File Extensions
G.2.4 Intended Usage
G.2.5 Author/Change Controller
G.3 Encoding Considerations
G.4 Recognizing XQuery Files
G.5 Charset Default Rules
G.6 Security Considerations
H Glossary (Non-Normative)
I Example Applications
(Non-Normative)
I.1 Joins
I.2 Queries on Sequence
I.3 Recursive Transformations
I.4 Selecting
Distinct Combinations
J Change Log (Non-Normative)
J.1 Substantive Changes
J.2 Incompatibilities
J.3 Editorial Changes
As increasing amounts of information are stored, exchanged, and presented using XML, the ability to intelligently query XML data sources becomes increasingly important. One of the great strengths of XML is its flexibility in representing many different kinds of information from diverse sources. To exploit this flexibility, an XML query language must provide features for retrieving and interpreting information from these diverse sources.
XQuery is designed to meet the requirements identified by the W3C XML Query Working Group [XQuery 3.0 Requirements] and the use cases in [XML Query Use Cases]. It is designed to be a language in which queries are concise and easily understood. It is also flexible enough to query a broad spectrum of XML information sources, including both databases and documents. The Query Working Group has identified a requirement for both a non-XML query syntax and an XML-based query syntax. XQuery is designed to meet the first of these requirements. XQuery is derived from an XML query language called Quilt [Quilt], which in turn borrowed features from several other languages, including XPath 1.0 [XML Path Language (XPath) Version 1.0], XQL [XQL], XML-QL [XML-QL], SQL [SQL], and OQL [ODMG].
[Definition: XQuery 3.0 operates on the abstract, logical structure of an XML document, rather than its surface syntax. This logical structure, known as the data model, is defined in [XQuery and XPath Data Model (XDM) 3.0].]
XQuery Version 3.0 is an extension of XPath Version 3.0. In general, any expression that is syntactically valid and executes successfully in both XPath 3.0 and XQuery 3.0 will return the same result in both languages. There are a few exceptions to this rule:
Because XQuery expands predefined entity references
and character references and XPath
does not, expressions containing these produce different results in
the two languages. For instance, the value of the string literal
"&"
is &
in XQuery, and
&
in XPath. (XPath is often embedded in other
languages, which may expand predefined entity references or
character references before the XPath expression is evaluated.)
If XPath 1.0 compatibility mode is enabled, XPath behaves differently from XQuery in a number of ways, which are discussed in [XML Path Language (XPath) 3.0].
Because these languages are so closely related, their grammars and language descriptions are generated from a common source to ensure consistency, and the editors of these specifications work together closely.
XQuery 3.0 also depends on and is closely related to the following specifications:
[XQuery and XPath Data Model (XDM) 3.0] defines the data model that underlies all XQuery 3.0 expressions.
The type system of XQuery 3.0 is based on XML Schema. It is implementation-defined whether the type system is based on [XML Schema 1.0] or [XML Schema 1.1].
The built-in function library and the operators supported by XQuery 3.0 are defined in [XQuery and XPath Functions and Operators 3.0].
One requirement in [XQuery 3.0 Requirements] is that an XML query language have both a human-readable syntax and an XML-based syntax. The XML-based syntax for XQuery is described in [XQueryX 3.0].
[Definition: An XQuery 3.0 Processor processes a query according to the XQuery 3.0 specification. ] [Definition: An XQuery 1.0 Processor processes a query according to the XQuery 1.0 specification. ]
[Definition: An XPath 3.0 Processor processes a query according to the XPath 3.0 specification.] [Definition: An XPath 2.0 Processor processes a query according to the XPath 2.0 specification.] [Definition: An XPath 1.0 Processor processes a query according to the XPath 1.0 specification.]
This document specifies a grammar for XQuery 3.0, using the same basic EBNF notation used in [XML 1.0]. Unless otherwise noted (see A.2 Lexical structure), whitespace is not significant in queries. Grammar productions are introduced together with the features that they describe, and a complete grammar is also presented in the appendix [A XQuery 3.0 Grammar]. The appendix is the normative version.
In the grammar productions in this document, named symbols are underlined and literal text is enclosed in double quotes. For example, the following productions describe the syntax of a function call:
[130] | FunctionCall |
::= | EQName ArgumentList |
[118] | ArgumentList |
::= | "(" (Argument (","
Argument)*)? ")" |
The productions should be read as follows: A function call consists of an EQName followed by an ArgumentList. The argument list consists of an opening parenthesis, an optional list of one or more arguments (separated by commas), and a closing parenthesis.
This document normatively defines the static and dynamic semantics of XQuery 3.0. In this document, examples and material labeled as "Note" are provided for explanatory purposes and are not normative.
Certain aspects of language processing are described in this specification as implementation-defined or implementation-dependent.
[Definition: Implementation-defined indicates an aspect that may differ between implementations, but must be specified by the implementor for each particular implementation.]
[Definition: Implementation-dependent indicates an aspect that may differ between implementations, is not specified by this or any W3C specification, and is not required to be specified by the implementor for any particular implementation.]
The basic building block of XQuery 3.0 is the expression, which is a string of [Unicode] characters; the version of Unicode to be used is implementation-defined. The language provides several kinds of expressions which may be constructed from keywords, symbols, and operands. In general, the operands of an expression are other expressions. XQuery 3.0 allows expressions to be nested with full generality. (However, unlike a pure functional language, it does not allow variable substitution if the variable declaration contains construction of new nodes.)
Note:
This specification contains no assumptions or requirements regarding the character set encoding of strings of [Unicode] characters.
Like XML, XQuery 3.0 is a case-sensitive language. Keywords in XQuery 3.0 use lower-case characters and are not reserved—that is, names in XQuery 3.0 expressions are allowed to be the same as language keywords, except for certain unprefixed function-names listed in A.3 Reserved Function Names.
[Definition:
In the data model, a
value is always a sequence.] [Definition: A sequence is
an ordered collection of zero or more items.] [Definition: An item is either an atomic value, a
node, or a function
itemDM30.] [Definition: An
atomic value is a value in the value space of an atomic
type, as defined in [XML Schema 1.0]
or [XML Schema 1.1].] [Definition: A node is an
instance of one of the node kinds defined in [XQuery and XPath Data Model (XDM) 3.0].]
Each node has a unique node identity, a typed value,
and a string value. In addition, some nodes have a
name. The typed value of a node is a sequence of zero
or more atomic values. The string value of a node is a value
of type xs:string
. The name of a node is a
value of type xs:QName
. [Definition: In certain
situations a property is said to be undefined This term
indicates that the property in question has no value and that any
attempt to use its value results in an error.] For example, the
context item may be undefined, or the typed value of an element
node may be undefined.
[Definition: A sequence containing exactly one item is called a singleton.] An item is identical to a singleton sequence containing that item. Sequences are never nested—for example, combining the values 1, (2, 3), and ( ) into a single sequence results in the sequence (1, 2, 3). [Definition: A sequence containing zero items is called an empty sequence.]
[Definition: The term XDM instance is used, synonymously with the term value, to denote an unconstrained sequence of items in the data model.]
In the XQuery 3.0 grammar, most names are specified using the EQName production, which allows lexical QNames, and also allows a namespace URI to be specified as a literal:
[192] | EQName |
::= | QName | URIQualifiedName |
[207] | QName |
::= | [http://www.w3.org/TR/REC-xml-names/#NT-QName]Names |
[208] | NCName |
::= | [http://www.w3.org/TR/REC-xml-names/#NT-NCName]Names |
[191] | URILiteral |
::= | StringLiteral |
[193] | URIQualifiedName |
::= | URILiteral ":"
NCName |
Names in XQuery 3.0 can be bound to namespaces, and are based on the syntax and semantics defined in [XML Names]. [Definition: A lexical QName is a name that conforms to the syntax of [http://www.w3.org/TR/REC-xml-names/#NT-QName].] A lexical QName consists of an optional namespace prefix and a local name. If the namespace prefix is present, it is separated from the local name by a colon. A lexical QName with a prefix can be converted into an expanded QName by resolving its namespace prefix to a namespace URI, using the statically known namespaces. The semantics of a lexical QName without a prefix depend on the expression in which it is found.
[Definition: An expanded QName consists
of an optional namespace URI and a local name. An expanded QName
also retains its original namespace prefix (if any), to facilitate
casting the expanded QName into a string.] The namespace URI value
is whitespace normalized according to the rules for the
xs:anyURI
type in [XML Schema
1.0] or [XML Schema 1.1]. Two
expanded
QNames are equal if their namespace URIs are equal and their
local names are equal (even if their namespace prefixes are not
equal). Namespace URIs and local names are compared on a codepoint
basis, without further normalization.
Here are some examples of EQNames:
pi
is a lexical QName without a namespace prefix.
math:pi
is a lexical QName with a namespace prefix.
"http://www.w3.org/2005/xpath-functions/math":pi
specifies the namespace URI using a URILiteral; it is not a lexical QName.
Certain namespace prefixes are predeclared by XQuery and bound to fixed namespace URIs. These namespace prefixes are as follows:
xml = http://www.w3.org/XML/1998/namespace
xs = http://www.w3.org/2001/XMLSchema
xsi = http://www.w3.org/2001/XMLSchema-instance
fn = http://www.w3.org/2005/xpath-functions
local =
http://www.w3.org/2005/xquery-local-functions
(see 4.18 Function Declaration.)
In addition to the prefixes in the above list,
this document uses the prefix err
to represent the
namespace URI http://www.w3.org/2005/xqt-errors
(see
2.3.2 Identifying and Reporting
Errors). This namespace prefix is not predeclared and its
use in this document is not normative.
Element nodes have a property called in-scope namespaces. [Definition: The in-scope namespaces property of an element node is a set of namespace bindings, each of which associates a namespace prefix with a URI.] For a given element, one namespace binding may have an empty prefix; the URI of this namespace binding is the default namespace within the scope of the element.
Note:
In [XML Path Language (XPath) Version 1.0], the in-scope namespaces of an element node are represented by a collection of namespace nodes arranged on a namespace axis, which is optional and deprecated in [XML Path Language (XPath) 3.0]. XQuery does not support the namespace axis and does not represent namespace bindings in the form of nodes. However, where other specifications such as [XSLT and XQuery Serialization 3.0] refer to namespace nodes, these nodes may be synthesized from the in-scope namespaces of an element node by interpreting each namespace binding as a namespace node.
[Definition: Within this specification, the term URI refers to a Universal Resource Identifier as defined in [RFC3986] and extended in [RFC3987] with the new name IRI.] The term URI has been retained in preference to IRI to avoid introducing new names for concepts such as "Base URI" that are defined or referenced across the whole family of XML specifications.
Note:
In most contexts, processors are not required to raise errors if a URI is not lexically valid according to [RFC3986] and [RFC3987]. See 2.4.5 URI Literals and 3.8.1.2 Namespace Declaration Attributes for details.
[Definition: The expression context for a given expression consists of all the information that can affect the result of the expression.] This information is organized into two categories called the static context and the dynamic context.
[Definition: The static context of an expression is the information that is available during static analysis of the expression, prior to its evaluation.] This information can be used to decide whether the expression contains a static error. If analysis of an expression relies on some component of the static context that has not been assigned a value, a static error is raised [err:XPST0001].
The individual components of the static context are summarized below. Rules governing the scope and initialization of these components can be found in C.1 Static Context Components.
[Definition: XPath 1.0
compatibility mode. This component must be
set by all host languages that include XPath 3.0 as a subset,
indicating whether rules for compatibility with XPath 1.0 are in
effect. XQuery sets the value of this component to
false
. ]
[Definition: Statically known
namespaces. This is a mapping from prefix to namespace
URI that defines all the namespaces that are known during
static processing of a given expression.] The URI value is
whitespace normalized according to the rules for the
xs:anyURI
type in [XML Schema
1.0] or [XML Schema 1.1]. Note the
difference between in-scope namespaces, which is a
dynamic property of an element node, and statically known namespaces, which is a
static property of an expression.
Some namespaces are predefined; additional namespaces can be added to the statically known namespaces by namespace declarations in a Prolog and by namespace declaration attributes in direct element constructors.
[Definition: Default
element/type namespace. This is a namespace URI or absentDM30.
The namespace URI, if present, is used for any unprefixed QName
appearing in a position where an element or type name is expected.]
The URI value is whitespace normalized according to the rules for
the xs:anyURI
type in [XML
Schema 1.0] or [XML Schema 1.1].
[Definition: Default function
namespace. This is a namespace URI or absentDM30.
The namespace URI, if present, is used for any unprefixed QName
appearing in a position where a function name is expected.] The URI
value is whitespace normalized according to the rules for the
xs:anyURI
type in [XML Schema
1.0] or [XML Schema 1.1].
[Definition: In-scope schema definitions. This is a generic term for all the element declarations, attribute declarations, and schema type definitions that are in scope during processing of an expression.] It includes the following three parts:
[Definition: In-scope schema types. Each schema type definition is identified either by an expanded QName (for a named type) or by an implementation-dependent type identifier (for an anonymous type). The in-scope schema types include the predefined schema types described in 2.5.1 Predefined Schema Types. If the Schema Import Feature is supported, in-scope schema types also include all type definitions found in imported schemas. ]
[Definition: In-scope element declarations. Each element declaration is identified either by an expanded QName (for a top-level element declaration) or by an implementation-dependent element identifier (for a local element declaration). If the Schema Import Feature is supported, in-scope element declarations include all element declarations found in imported schemas. ] An element declaration includes information about the element's substitution group affiliation.
[Definition: Substitution groups are defined in [XML Schema 1.0] and [XML Schema 1.1] Part 1. Informally, the substitution group headed by a given element (called the head element) consists of the set of elements that can be substituted for the head element without affecting the outcome of schema validation.]
[Definition: In-scope attribute declarations. Each attribute declaration is identified either by an expanded QName (for a top-level attribute declaration) or by an implementation-dependent attribute identifier (for a local attribute declaration). If the Schema Import Feature is supported, in-scope attribute declarations include all attribute declarations found in imported schemas. ]
[Definition: In-scope variables. This is a mapping from expanded QName to type. It defines the set of variables that are available for reference within an expression. The expanded QName is the name of the variable, and the type is the static type of the variable.]
Variable declarations in a Prolog are added to in-scope
variables. An expression that binds a variable (such as
a let
, for
, some
, or
every
expression) extends the in-scope
variables of its subexpressions with the new bound variable and
its type. Within the body of an inline function or
user-defined
function , the in-scope variables are extended by the
names and types of the function parameters.
The static type of a variable may either be declared in a query or inferred by static type inference as discussed in 2.2.3.1 Static Analysis Phase.
[Definition: Context item static type. This component defines the static type of the context item within the scope of a given expression.]
[Definition: Function signatures. This component defines the set of functions that are available to be called from within an expression. Each function is uniquely identified by its expanded QName and its arity (number of parameters).] In addition to the name and arity, each function signature specifies the static types of the function parameters and result.
The function signatures include the signatures of functions from a variety of sources, including built-in functions described in [XQuery and XPath Functions and Operators 3.0], functions declared in the current module (see 4.18 Function Declaration), module imports (see 4.12 Module Import), constructor functions (see 3.15.5 Constructor Functions), and functions provided by an implementation or via an implementation-defined API (see C.1 Static Context Components). It is a static error [err:XQST0034] if two such functions have the same expanded QName and the same arity (even if the signatures are consistent).
[Definition: Statically known collations. This is an implementation-defined mapping from URI to collation. It defines the names of the collations that are available for use in processing queries and expressions.] [Definition: A collation is a specification of the manner in which strings and URIs are compared and, by extension, ordered. For a more complete definition of collation, see [XQuery and XPath Functions and Operators 3.0].]
[Definition: Default collation. This
identifies one of the collations in statically known collations as the
collation to be used by functions and operators for comparing and
ordering values of type xs:string
and
xs:anyURI
(and types derived from them) when no
explicit collation is specified.]
[Definition: Construction mode. The
construction mode governs the behavior of element and document node
constructors. If construction mode is preserve
, the
type of a constructed element node is xs:anyType
, and
all attribute and element nodes copied during node construction
retain their original types. If construction mode is
strip
, the type of a constructed element node is
xs:untyped
; all element nodes copied during node
construction receive the type xs:untyped
, and all
attribute nodes copied during node construction receive the type
xs:untypedAtomic
.]
[Definition: Ordering mode. Ordering
mode, which has the value ordered
or
unordered
, affects the ordering of the result sequence
returned by certain expressions, as discussed in 3.10 Ordered and Unordered
Expressions. ]
[Definition:
Default order for empty sequences. This component controls
the processing of empty sequences and NaN
values as
ordering keys in an order by
clause in a FLWOR
expression, as described in 3.9.8
Order By Clause.] Its value may be greatest
or
least
.
[Definition: Boundary-space
policy. This component controls the processing of boundary
whitespace by direct element constructors, as
described in 3.8.1.4 Boundary
Whitespace.] Its value may be preserve
or
strip
.
[Definition: Copy-namespaces
mode. This component controls the namespace bindings that are
assigned when an existing element node is copied by an element
constructor, as described in 3.8.1 Direct Element
Constructors. Its value consists of two parts:
preserve
or no-preserve
, and
inherit
or no-inherit
.]
[Definition: Static Base URI. This is
an absolute URI, used to resolve relative URIs during static
analysis.] The URI value is whitespace normalized according to the
rules for the xs:anyURI
type in [XML Schema 1.0] or [XML
Schema 1.1]. The Static Base URI can be
set using a Base URI Declaration.
[Definition: Statically known
documents. This is a mapping from strings to types. The string
represents the absolute URI of a resource that is potentially
available using the fn:doc
function. The type is the
static type of a
call to fn:doc
with the given URI as its literal
argument. ] If the argument to fn:doc
is a string
literal that is not present in statically known documents,
then the static
type of fn:doc
is
document-node()?
.
Note:
The purpose of the statically known documents is to
provide static type information, not to determine which documents
are available. A URI need not be found in the statically known
documents to be accessed using fn:doc
.
[Definition: Statically known
collections. This is a mapping from strings to types. The
string represents the absolute URI of a resource that is
potentially available using the fn:collection
function. The type is the type of the sequence of nodes that would
result from calling the fn:collection
function with
this URI as its argument.] If the argument to
fn:collection
is a string literal that is not present
in statically known collections, then the static type of
fn:collection
is node()*
.
Note:
The purpose of the statically known collections is to
provide static type information, not to determine which collections
are available. A URI need not be found in the statically known
collections to be accessed using
fn:collection
.
[Definition:
Statically known default collection type. This is the type
of the sequence of nodes that would result from calling the
fn:collection
function with no arguments.] Unless
initialized to some other value by an implementation, the value of
statically known default collection type is
node()*
.
[Definition: Statically
known decimal formats. This is a mapping from EQName to decimal format, with one
default format that has no visible name. Each format is used
for serializing decimal numbers using
fn:format-number()
.]
Each decimal format contains the following properties,
which control the interpretation of characters in the
picture string supplied to the fn:format-number
function, and also specify characters that may appear in the result
of formatting the number. In each case the value must be a single
character:
[Definition: decimal-separator specifies the character used for the decimal-separator-sign; the default value is the period character (.)]
[Definition: grouping-separator specifies the character used for the grouping-sign, which is typically used as a thousands separator; the default value is the comma character (,)]
[Definition: percent-sign specifies the character used for the percent-sign; the default value is the percent character (%)]
[Definition: per-mille-sign specifies the character used for the per-mille-sign; the default value is the Unicode per-mille character (#x2030)]
[Definition: zero-digit specifies the character used for the digit-zero-sign; the default value is the digit zero (0). This character must be a digit (category Nd in the Unicode property database), and it must have the numeric value zero. This attribute implicitly defines the Unicode character that is used to represent each of the values 0 to 9 in the final result string: Unicode is organized so that each set of decimal digits forms a contiguous block of characters in numerical sequence.]
The following attributes control the interpretation of characters in the picture string supplied to the format-number function. In each case the value must be a single character.
[Definition: digit-sign specifies the character used for the digit-sign in the picture string; the default value is the number sign character (#)]
[Definition: pattern-separator-sign specifies the character used for the pattern-separator-sign, which separates positive and negative sub-pictures in a picture string; the default value is the semi-colon character (;)]
The following attributes specify characters or strings that may appear in the result of formatting the number:
[Definition: infinity specifies the string used for the infinity-symbol; the default value is the string "Infinity"]
[Definition: NaN specifies the string used for the NaN-symbol, which is used to represent the value NaN (not-a-number); the default value is the string "NaN"]
[Definition: minus-sign specifies the character used for the minus-symbol; the default value is the hyphen-minus character (-, #x2D). The value must be a single character.]
[Definition: The dynamic context of an expression is defined as information that is available at the time the expression is evaluated.] If evaluation of an expression relies on some part of the dynamic context that has not been assigned a value, a dynamic error is raised [err:XPDY0002].
The individual components of the dynamic context are summarized below. Further rules governing the semantics of these components can be found in C.2 Dynamic Context Components.
The dynamic context consists of all the components of the static context, and the additional components listed below.
[Definition: The first three components of the dynamic context (context item, context position, and context size) are called the focus of the expression. ] The focus enables the processor to keep track of which items are being processed by the expression.
Certain language constructs, notably the path expression
E1/E2
and the predicate E1[E2]
, create a new
focus for the evaluation of a sub-expression. In these constructs,
E2
is evaluated once for each item in the sequence
that results from evaluating E1
. Each time
E2
is evaluated, it is evaluated with a different
focus. The focus for evaluating E2
is referred to
below as the inner focus, while the focus for evaluating
E1
is referred to as the outer focus. The inner
focus exists only while E2
is being evaluated. When
this evaluation is complete, evaluation of the containing
expression continues with its original focus unchanged.
[Definition: The context item is the
item currently being
processed.] [Definition: When the context item is a node, it
can also be referred to as the context node.] The context
item is returned by an expression consisting of a single dot
(.
). When an expression E1/E2
or
E1[E2]
is evaluated, each item in the sequence
obtained by evaluating E1
becomes the context item in
the inner focus for an evaluation of E2
.
[Definition: The context position is
the position of the context item within the sequence of items
currently being processed.] It changes whenever the context item
changes. When the focus is defined, the value of the context
position is an integer greater than zero. The context position is
returned by the expression fn:position()
. When an
expression E1/E2
or E1[E2]
is evaluated,
the context position in the inner focus for an evaluation of
E2
is the position of the context item in the sequence
obtained by evaluating E1
. The position of the first
item in a sequence is always 1 (one). The context position is
always less than or equal to the context size.
[Definition: The context size is the
number of items in the sequence of items currently being
processed.] Its value is always an integer greater than zero. The
context size is returned by the expression fn:last()
.
When an expression E1/E2
or E1[E2]
is
evaluated, the context size in the inner focus for an evaluation of
E2
is the number of items in the sequence obtained by
evaluating E1
.
[Definition: Dynamic Base URI. This is
an absolute URI, used to resolve relative URIs during dynamic
evaluation.] The URI value is whitespace normalized according to
the rules for the xs:anyURI
type in [XML Schema 1.0] or [XML
Schema 1.1]. The Dynamic Base URI corresponds to the location
in which the query is executed; it is set by the
implementation.
[Definition: Variable values. This is a mapping from expanded QName to value. It contains the same expanded QNames as the in-scope variables in the static context for the expression. The expanded QName is the name of the variable and the value is the dynamic value of the variable, which includes its dynamic type.]
[Definition: Function implementations. Each function in function signatures has a function implementation that enables the function to map instances of its parameter types into an instance of its result type. For a user-defined function, the function implementation is an XQuery expression. For a built-in function or external function, the function implementation is implementation-dependent. ]
[Definition: Current dateTime. This
information represents an implementation-dependent point
in time during the processing of a
query, and includes an explicit timezone. It can be
retrieved by the fn:current-dateTime
function. If
invoked multiple times during the execution of a query, this function always returns the same
result.]
[Definition: Implicit timezone. This
is the timezone to be used when a date, time, or dateTime value
that does not have a timezone is used in a comparison or arithmetic
operation. The implicit timezone is an implementation-defined value of
type xs:dayTimeDuration
. See [XML Schema 1.0] or [XML
Schema 1.1] for the range of valid values of a timezone.]
[Definition: Available documents.
This is a mapping of strings to document nodes. The string
represents the absolute URI of a resource. The document node is the
root of a tree that represents that resource using the data model. The document node
is returned by the fn:doc
function when applied to
that URI.] The set of available documents is not limited to the set
of statically known documents, and it may be
empty.
If there are one or more URIs in available documents that map to a
document node D
, then the document-uri property of
D
must either be absent, or must be one of these
URIs.
Note:
This means that given a document node $N
, the
result of fn:doc(fn:document-uri($N)) is $N
will
always be true
, unless
fn:document-uri($N)
is an empty sequence.
[Definition: Available
collections. This is a mapping of strings to sequences of
nodes. The string represents the absolute URI of a resource. The
sequence of nodes represents the result of the
fn:collection
function when that URI is supplied as
the argument. ] The set of available collections is not limited to
the set of statically known collections, and it
may be empty.
For every document node D
that is in the target of
a mapping in available collections, or that is
the root of a tree containing such a node, the document-uri
property of D
must either be absent, or must be a URI
U
such that available documents contains a mapping
from U
to D
."
Note:
This means that for any document node $N
retrieved
using the fn:collection
function, either directly or
by navigating to the root of a node that was returned, the result
of fn:doc(fn:document-uri($N)) is $N
will always be
true
, unless fn:document-uri($N)
is an
empty sequence. This implies a requirement for the
fn:doc
and fn:collection
functions to be
consistent in their effect. If the implementation uses catalogs or
user-supplied URI resolvers to dereference URIs supplied to the
fn:doc
function, the implementation of the
fn:collection
function must take these mechanisms into
account. For example, an implementation might achieve this by
mapping the collection URI to a set of document URIs, which are
then resolved using the same catalog or URI resolver that is used
by the fn:doc
function.
[Definition: Default
collection. This is the sequence of nodes that would result
from calling the fn:collection
function with no
arguments.] The value of default collection may be
initialized by the implementation.
[Definition: Environment variables. This is a mapping from names to values. Both the names and the values are strings. The names are compared using an implementation-defined collation, and are unique under this collation. The set of environment variables is implementation-defined and may be empty.]
Note:
A possible implementation is to provide the set of POSIX environment variables (or their equivalent on other operating systems) appropriate to the process in which the query is initiated.
XQuery 3.0 is defined in terms of the data model and the expression context.
Figure 1: Processing Model Overview
Figure 1 provides a schematic overview of the processing steps that are discussed in detail below. Some of these steps are completely outside the domain of XQuery 3.0; in Figure 1, these are depicted outside the line that represents the boundaries of the language, an area labeled external processing. The external processing domain includes generation of an XDM instance that represents the data to be queried (see 2.2.1 Data Model Generation), schema import processing (see 2.2.2 Schema Import Processing) and serialization (see 2.2.4 Serialization). The area inside the boundaries of the language is known as the query processing domain , which includes the static analysis and dynamic evaluation phases (see 2.2.3 Expression Processing). Consistency constraints on the query processing domain are defined in 2.2.5 Consistency Constraints.
Before a query can be processed, its input data must be represented as an XDM instance. This process occurs outside the domain of XQuery 3.0, which is why Figure 1 represents it in the external processing domain. Here are some steps by which an XML document might be converted to an XDM instance:
A document may be parsed using an XML parser that generates an XML Information Set (see [XML Infoset]). The parsed document may then be validated against one or more schemas. This process, which is described in [XML Schema 1.0] or [XML Schema 1.1], results in an abstract information structure called the Post-Schema Validation Infoset (PSVI). If a document has no associated schema, its Information Set is preserved. (See DM1 in Fig. 1.)
The Information Set or PSVI may be transformed into an XDM instance by a process described in [XQuery and XPath Data Model (XDM) 3.0]. (See DM2 in Fig. 1.)
The above steps provide an example of how an XDM instance might be constructed. An XDM instance might also be synthesized directly from a relational database, or constructed in some other way (see DM3 in Fig. 1.) XQuery 3.0 is defined in terms of the data model, but it does not place any constraints on how XDM instances are constructed.
[Definition: Each element node and attribute
node in an XDM instance has a type
annotation ( described in [XQuery and XPath Data Model (XDM) 3.0].
) The type annotation of a node is a reference to an XML
Schema type. ] The type-name
of a node is
the name of the type referenced by its type annotation. If the
XDM
instance was derived from a validated XML document as described
in Section 3.3
Construction from a PSVI DM30, the
type annotations of the element and attribute nodes are derived
from schema validation. XQuery 3.0 does not provide a way to
directly access the type annotation of an element or attribute
node.
The value of an attribute is represented directly within the
attribute node. An attribute node whose type is unknown (such as
might occur in a schemaless document) is given the type annotation
xs:untypedAtomic
.
The value of an element is represented by the children of the
element node, which may include text nodes and other element nodes.
The type
annotation of an element node indicates how the values in its
child text nodes are to be interpreted. An element that has not
been validated (such as might occur in a schemaless document) is
annotated with the schema type xs:untyped
. An element
that has been validated and found to be partially valid is
annotated with the schema type xs:anyType
. If an
element node is annotated as xs:untyped
, all its
descendant element nodes are also annotated as
xs:untyped
. However, if an element node is annotated
as xs:anyType
, some of its descendant element nodes
may have a more specific type annotation.
The in-scope schema definitions in the static context may be extracted from actual XML schemas (see step SI1 in Figure 1) or may be generated by some other mechanism (see step SI2 in Figure 1). In either case, the result must satisfy the consistency constraints defined in 2.2.5 Consistency Constraints.
XQuery 3.0 defines two phases of processing called the static analysis phase and the dynamic evaluation phase (see Fig. 1). During the static analysis phase, static errors, dynamic errors, or type errors may be raised. During the dynamic evaluation phase, only dynamic errors or type errors may be raised. These kinds of errors are defined in 2.3.1 Kinds of Errors.
Within each phase, an implementation is free to use any strategy or algorithm whose result conforms to the specifications in this document.
[Definition: The static analysis phase depends on the expression itself and on the static context. The static analysis phase does not depend on input data (other than schemas).]
During the static analysis phase, the query is parsed into an internal representation called the operation tree (step SQ1 in Figure 1). A parse error is raised as a static error [err:XPST0003]. The static context is initialized by the implementation (step SQ2). The static context is then changed and augmented based on information in the prolog (step SQ3). If the Schema Import Feature is supported, the in-scope schema definitions are populated with information from imported schemas. If the Module Feature is supported, the static context is extended with function declarations and variable declarations from imported modules. The static context is used to resolve schema type names, function names, namespace prefixes, and variable names (step SQ4). If a name of one of these kinds in the operation tree is not found in the static context, a static error ([err:XPST0008] or [err:XPST0017]) is raised (however, see exceptions to this rule in 2.5.5.3 Element Test and 2.5.5.5 Attribute Test.)
The operation tree is then normalized by making explicit the implicit operations such as atomization and extraction of Effective Boolean Values (step SQ5).
During the static analysis phase, an XQuery processor may perform type analysis. The effect of type analysis is to assign a static type to each expression in the operation tree. [Definition: The static type of an expression is the best inference that the processor is able to make statically about the type of the result of the expression.] This specification does not define the rules for type analysis nor the static types that are assigned to particular expressions: the only constraint is that the inferred type must match all possible values that the expression is capable of returning.
Examples of inferred static types might be:
For the expression concat(a,b)
the inferred static
type is xs:string
For the expression $a = $v
the inferred static type
is xs:boolean
For the expression $s[exp]
the inferred static type
has the same item type as the static type of $s
, but a
cardinality that allows the empty sequence even if the static type
of $s
does not allow an empty sequence.
The inferred static type of the expression data($x)
(whether written explicitly or inserted into the operation tree in
places where atomization is implicit) depends on the inferred
static type of $x
: for example, if $x
has
type element(*, xs:integer)
then data($x)
has static type xs:integer
.
In XQuery 1.0 and XPath 2.0, rules for static type inferencing were published normatively in [XQuery 1.0 and XPath 2.0 Formal Semantics], but implementations were allowed to refine these rules to infer a more precise type where possible. In XQuery 3.0 and XPath 3.0, the rules for static type inferencing are entirely implementation-defined.
Every kind of expression also imposes requirements on the type
of its operands. For example, with the expression
substring($a, $b, $c)
, $a
must be of type
xs:string
(or something that can be converted to
xs:string
by the function calling rules), while
$b
and $c
must be of type
xs:double
.
If the Static Typing Feature is in effect, an XQuery processor
must signal a type error during static analysis if the inferred
static type of an expression is not subsumed by the required type
of the context where the expression is used. For example, the call
of substring above would cause a type error if the inferred static
type of $a
is xs:integer
; equally, a type
error would be reported during static analysis if the inferred
static type is xs:anyAtomicType
.
If the Static Typing Feature is not in effect, a processor may
signal a type error during static analysis only if the inferred
static type of an expression has no overlap (intersection) with the
required type: so for the first argument of substring, the
processor may report an error if the inferred type is
xs:integer
, but not if it is
xs:anyAtomicType
. Alternatively, if the Static Typing
Feature is not in effect, the processor may defer all type checking
until the dynamic evaluation phase.
[Definition: The dynamic evaluation phase is the phase during which the value of an expression is computed.] It occurs after completion of the static analysis phase.
The dynamic evaluation phase can occur only if no errors were detected during the static analysis phase. If the Static Typing Feature is in effect, all type errors are detected during static analysis and serve to inhibit the dynamic evaluation phase.
The dynamic evaluation phase depends on the operation tree of the expression being evaluated (step DQ1), on the input data (step DQ4), and on the dynamic context (step DQ5), which in turn draws information from the external environment (step DQ3) and the static context (step DQ2). The dynamic evaluation phase may create new data-model values (step DQ4) and it may extend the dynamic context (step DQ5)—for example, by binding values to variables.
[Definition: A dynamic type is associated
with each value as it is computed. The dynamic type of a value may
be more specific than the static type of the expression that computed
it (for example, the static type of an expression might be
xs:integer*
, denoting a sequence of zero or more
integers, but at evaluation time its value may have the dynamic
type xs:integer
, denoting exactly one integer.)]
If an operand of an expression is found to have a dynamic type that is not appropriate for that operand, a type error is raised [err:XPTY0004].
Even though static typing can catch many type errors before an expression is
executed, it is possible for an expression to raise an error during
evaluation that was not detected by static analysis. For example,
an expression may contain a cast of a string into an integer, which
is statically valid. However, if the actual value of the string at
run time cannot be cast into an integer, a dynamic error will result. Similarly,
an expression may apply an arithmetic operator to a value whose
static type is
xs:untypedAtomic
. This is not a static error, but at run
time, if the value cannot be successfully cast to a numeric type, a dynamic error will be
raised.
When the Static Typing Feature is in effect, it is also possible for static analysis of an expression to raise a type error, even though execution of the expression on certain inputs would be successful. For example, an expression might contain a function that requires an element as its parameter, and the static analysis phase might infer the static type of the function parameter to be an optional element. This case is treated as a type error and inhibits evaluation, even though the function call would have been successful for input data in which the optional element is present.
[Definition: Serialization is the process of converting an XDM instance into a sequence of octets (step DM4 in Figure 1.) ] The general framework for serialization is described in [XSLT and XQuery Serialization 3.0].
An XQuery implementation is not required to provide a serialization interface. For example, an implementation may only provide a DOM interface (see [Document Object Model]) or an interface based on an event stream. In these cases, serialization would be outside of the scope of this specification.
[XSLT and XQuery Serialization 3.0] defines a set of serialization parameters that govern the serialization process. If an XQuery implementation provides a serialization interface, it may support (and may expose to users) any of the serialization parameters listed (with default values) in C.1 Static Context Components.
[Definition: An output declaration is an option declaration in the namespace "http://www.w3.org/2010/xslt-xquery-serialization"; it is used to declare serialization parameters.] When the application requests serialization of the output, the processor may use these parameters to control the way in which the serialization takes place. Processors may also allow external mechanisms for specifying serialization parameters, which may or may not override serialization parameters specified in the query prolog.
declare namespace output = "http://www.w3.org/2010/xslt-xquery-serialization"; declare option output:method "xml"; declare option output:encoding "iso-8859-1"; declare option output:indent "yes"; declare option output:parameter-document "file:///home/me/serialization-parameters.xml";
An output declaration may appear only in a
main module; it is a static error [err:XQST0108] if an output declaration appears
in a library
module. It is a static error [err:XQST0110] if the same serialization
parameter is declared more than once. It is a static error [err:XQST0109] if the local
name of an output declaration in the
http://www.w3.org/2010/xslt-xquery-serialization
namespace is not one of the serialization parameter names listed in
C.1 Static Context
Components or parameter-document
. The default
value for the method parameter is "xml". An implementation may
define additional implementation-defined
serialization parameters in its own namespaces.
If the local name of an output declaration in the
http://www.w3.org/2010/xslt-xquery-serialization
namespace is parameter-document
, the value of the
output declaration is treated as a URI literal. The value is a
location hint, and identifies an XDM instance in an
implementation-defined way. If a processor is performing
serialization, it is a static error [err:XQST0119] if the implementation is not able
to process the value of the output:parameter-document
declaration to produce an XDM instance.
If a processor is performing serialization, the XDM instance
identified by an output:parameter-document
output
declaration specifies the values of serialization parameters in the
manner defined by
Section 3.1 Setting Serialization Parameters by Means of a Data
Model Instance SER30. It is a static
error [err:XQST0115] if this yields a serialization
error. The value of any other output declaration overrides any
value that might have been specified for the same serialization
parameter using an output declaration in the
http://www.w3.org/2010/xslt-xquery-serialization
namespace with the local name parameter-document declaration.
A serialization parameter that is not applicable to the chosen output method must be ignored, except that if its value is not a valid value for that parameter, the error may be reported.
A processor that is performing serialization must report a serialization error if the values of any serialization parameters (other than any that are ignored under the previous paragraph) are incorrect.
A processor that is not performing serialization may report errors if any serialization parameters are incorrect, or may ignore such parameters.
Specifying serialization parameters in a query does not by itself demand that the output be serialized. It merely defines the desired form of the serialized output for use in situations where the processor has been asked to perform serialization.
Note:
The data model permits an element node to have fewer in-scope namespaces than its parent. Correct serialization of such an element node would require "undeclaration" of namespaces, which is a feature of [XML Names 1.1]. An implementation that does not support [XML Names 1.1] is permitted to serialize such an element without "undeclaration" of namespaces, which effectively causes the element to inherit the in-scope namespaces of its parent.
In order for XQuery 3.0 to be well defined, the input XDM instance, the static context, and the dynamic context must be mutually consistent. The consistency constraints listed below are prerequisites for correct functioning of an XQuery 3.0 implementation. Enforcement of these consistency constraints is beyond the scope of this specification. This specification does not define the result of a query under any condition in which one or more of these constraints is not satisfied.
For every node that has a type annotation, if that type annotation is found in the in-scope schema definitions (ISSD), then its definition in the ISSD must be equivalent to its definition in the type annotation .
Every element name, attribute name, or schema type name referenced in in-scope variables or function signatures must be in the in-scope schema definitions, unless it is an element name referenced as part of an ElementTest or an attribute name referenced as part of an AttributeTest.
Any reference to a global element, attribute, or type name in the in-scope schema definitions must have a corresponding element, attribute or type definition in the in-scope schema definitions.
For each mapping of a string to a document node in available documents, if there exists a mapping of the same string to a document type in statically known documents, the document node must match the document type, using the matching rules in 2.5.5 SequenceType Matching.
For each mapping of a string to a sequence of nodes in available collections, if there exists a mapping of the same string to a type in statically known collections, the sequence of nodes must match the type, using the matching rules in 2.5.5 SequenceType Matching.
The sequence of nodes in the default collection must match the statically known default collection type, using the matching rules in 2.5.5 SequenceType Matching.
The value of the context item must match the context item static type, using the matching rules in 2.5.5 SequenceType Matching.
For each (variable, type) pair in in-scope variables and the corresponding (variable, value) pair in variable values such that the variable names are equal, the value must match the type, using the matching rules in 2.5.5 SequenceType Matching.
For each variable declared as external, if the variable declaration does not include a VarDefaultValue, the external environment must provide a value for the variable.
For each variable declared as external for which the external environment provides a value: If the variable declaration includes a declared type, the value provided by the external environment must match the declared type, using the matching rules in 2.5.5 SequenceType Matching. If the variable declaration does not include a declared type, the external environment must provide a type to accompany the value provided, using the same matching rules.
For each variable declared as external
: If the
variable declaration includes a declared type, the external
environment must provide a value for the variable that matches the
declared type, using the matching rules in 2.5.5 SequenceType Matching.
If the variable declaration does not include a declared type, the
external environment may provide a value of any type, using the
same matching rules.
For each function declared as external: the function implementation must either return a value that matches the declared result type, using the matching rules in 2.5.5 SequenceType Matching, or raise an implementation-defined error.
For a given query, define a participating ISSD as the in-scope schema definitions of a module that is used in evaluating the query. If two participating ISSDs contain a definition for the same schema type, element name, or attribute name, the definitions must be equivalent in both ISSDs. Furthermore, if two participating ISSDs each contain a definition of a schema type T, the set of types derived by extension from T must be equivalent in both ISSDs. Also, if two participating ISSDs each contain a definition of an element name E, the substitution group headed by E must be equivalent in both ISSDs.
In the statically known namespaces, the prefix
xml
must not be bound to any namespace URI other than
http://www.w3.org/XML/1998/namespace
, and no prefix
other than xml
may be bound to this namespace URI. The
prefix xmlns
must not be bound to any namespace URI,
and no prefix may be bound to the namespace URI
http://www.w3.org/2000/xmlns/
.
As described in 2.2.3 Expression Processing, XQuery 3.0 defines a static analysis phase, which does not depend on input data, and a dynamic evaluation phase, which does depend on input data. Errors may be raised during each phase.
[Definition: A static error is an error that must be detected during the static analysis phase. A syntax error is an example of a static error.]
[Definition: A dynamic error is an error that must be detected during the dynamic evaluation phase and may be detected during the static analysis phase. Numeric overflow is an example of a dynamic error. ]
[Definition: A type error may be raised during the static analysis phase or the dynamic evaluation phase. During the static analysis phase, a type error occurs when the static type of an expression does not match the expected type of the context in which the expression occurs. During the dynamic evaluation phase, a type error occurs when the dynamic type of a value does not match the expected type of the context in which the value occurs.]
The outcome of the static analysis phase is either success or one or more type errors, static errors, or statically-detected dynamic errors. The result of the dynamic evaluation phase is either a result value, a type error, or a dynamic error.
If more than one error is present, or if an error condition comes within the scope of more than one error defined in this specification, then any non-empty subset of these errors may be reported.
During the static analysis phase, if the Static
Typing Feature is in effect and the static type assigned to an expression
other than ()
or data(())
is
empty-sequence()
, a static error is raised [err:XPST0005]. This catches
cases in which a query refers to an element or attribute that is
not present in the in-scope schema definitions, possibly because of a
spelling error.
Independently of whether the Static Typing Feature is in effect, if an implementation can determine during the static analysis phase that a QueryBody , if evaluated, would necessarily raise a dynamic error or that an expression, if evaluated, would necessarily raise a type error, the implementation may (but is not required to) report that error during the static analysis phase.
Note:
An implementation can raise a dynamic error for a QueryBody statically only if the query can never execute without raising that error, as in the following example:
error()
The following example contains a type error, which can be reported statically even if the implementation can not prove that the expression will actually be evaluated.
if (empty($arg)) then "cat" * 2 else 0
[Definition: In addition to static errors, dynamic errors, and type errors, an XQuery 3.0 implementation may raise warnings, either during the static analysis phase or the dynamic evaluation phase. The circumstances in which warnings are raised, and the ways in which warnings are handled, are implementation-defined.]
In addition to the errors defined in this specification, an implementation may raise a dynamic error for a reason beyond the scope of this specification. For example, limitations may exist on the maximum numbers or sizes of various objects. Any such limitations, and the consequences of exceeding them, are implementation-dependent.
The errors defined in this specification are identified by
QNames that have the form err:XXYYnnnn
, where:
err
denotes the namespace for XPath and XQuery
errors, http://www.w3.org/2005/xqt-errors
. This
binding of the namespace prefix err
is used for
convenience in this document, and is not normative.
XX
denotes the language in which the error is
defined, using the following encoding:
XP
denotes an error defined by XPath. Such an error
may also occur XQuery since XQuery includes XPath as a subset.
XQ
denotes an error defined by XQuery.
YY
denotes the error category, using the following
encoding:
ST
denotes a static error.
DY
denotes a dynamic error.
TY
denotes a type error.
nnnn
is a unique numeric code.
Note:
The namespace URI for XPath and XQuery errors is not expected to change from one version of XQuery to another. However, the contents of this namespace may be extended to include additional error definitions.
The method by which an XQuery 3.0 processor reports error information to the external environment is implementation-defined.
An error can be represented by a URI reference that is derived
from the error QName as follows: an error with namespace URI
NS
and local part LP
can be represented as the URI reference NS
#
LP
. For example, an error
whose QName is err:XPST0017
could be represented as
http://www.w3.org/2005/xqt-errors#XPST0017
.
Note:
Along with a code identifying an error, implementations may wish to return additional information, such as the location of the error or the processing phase in which it was detected. If an implementation chooses to do so, then the mechanism that it uses to return this information is implementation-defined.
Except as noted in this document, if any operand of an
expression raises a dynamic error, the expression also raises a
dynamic
error. If an expression can validly return a value or raise a
dynamic error, the implementation may choose to return the value or
raise the dynamic error. For example, the logical expression
expr1 and expr2
may return the value
false
if either operand returns false
, or
may raise a dynamic error if either operand raises a dynamic
error.
If more than one operand of an expression raises an error, the implementation may choose which error is raised by the expression. For example, in this expression:
($x div $y) + xs:decimal($z)
both the sub-expressions ($x div $y)
and
xs:decimal($z)
may raise an error. The implementation
may choose which error is raised by the "+
"
expression. Once one operand raises an error, the implementation is
not required, but is permitted, to evaluate any other operands.
[Definition: In addition to its identifying QName, a dynamic error may also carry a descriptive string and one or more additional values called error values.] An implementation may provide a mechanism whereby an application-defined error handler can process error values and produce diagnostic messages.
A dynamic error may be raised by a built-in function or operator. For
example, the div
operator raises an error if its
operands are xs:decimal
values and its second operand
is equal to zero. Errors raised by built-in functions and operators
are defined in [XQuery and XPath
Functions and Operators 3.0].
A dynamic error can also be raised explicitly by calling the
fn:error
function, which only raises an error and
never returns a value. This function is defined in [XQuery and XPath Functions and Operators
3.0]. For example, the following function call raises a dynamic
error, providing a QName that identifies the error, a descriptive
string, and a diagnostic value (assuming that the prefix
app
is bound to a namespace containing
application-defined error codes):
fn:error(xs:QName("app:err057"), "Unexpected value", fn:string($v))
Because different implementations may choose to evaluate or optimize an expression in different ways, certain aspects of the detection and reporting of dynamic errors are implementation-dependent, as described in this section.
An implementation is always free to evaluate the operands of an operator in any order.
In some cases, a processor can determine the result of an
expression without accessing all the data that would be implied by
the formal expression semantics. For example, the formal
description of filter expressions suggests that
$s[1]
should be evaluated by examining all the items
in sequence $s
, and selecting all those that satisfy
the predicate position()=1
. In practice, many
implementations will recognize that they can evaluate this
expression by taking the first item in the sequence and then
exiting. If $s
is defined by an expression such as
//book[author eq 'Berners-Lee']
, then this strategy
may avoid a complete scan of a large document and may therefore
greatly improve performance. However, a consequence of this
strategy is that a dynamic error or type error that would be
detected if the expression semantics were followed literally might
not be detected at all if the evaluation exits early. In this
example, such an error might occur if there is a book
element in the input data with more than one author
subelement.
The extent to which a processor may optimize its access to data, at the cost of not detecting errors, is defined by the following rules.
Consider an expression Q that has an operand (sub-expression) E. In general the value of E is a sequence. At an intermediate stage during evaluation of the sequence, some of its items will be known and others will be unknown. If, at such an intermediate stage of evaluation, a processor is able to establish that there are only two possible outcomes of evaluating Q, namely the value V or an error, then the processor may deliver the result V without evaluating further items in the operand E. For this purpose, two values are considered to represent the same outcome if their items are pairwise the same, where nodes are the same if they have the same identity, and values are the same if they are equal and have exactly the same type.
There is an exception to this rule: If a processor evaluates an
operand E (wholly or in part), then it is required to
establish that the actual value of the operand E does not
violate any constraints on its cardinality. For example, the
expression $e eq 0
results in a type error if the
value of $e
contains two or more items. A processor is
not allowed to decide, after evaluating the first item in the value
of $e
and finding it equal to zero, that the only
possible outcomes are the value true
or a type error
caused by the cardinality violation. It must establish that the
value of $e
contains no more than one item.
These rules apply to all the operands of an expression considered in combination: thus if an expression has two operands E1 and E2, it may be evaluated using any samples of the respective sequences that satisfy the above rules.
The rules cascade: if A is an operand of B and B is an operand of C, then the processor needs to evaluate only a sufficient sample of B to determine the value of C, and needs to evaluate only a sufficient sample of A to determine this sample of B.
The effect of these rules is that the processor is free to stop
examining further items in a sequence as soon as it can establish
that further items would not affect the result except possibly by
causing an error. For example, the processor may return
true
as the result of the expression S1 =
S2
as soon as it finds a pair of equal values from the two
sequences.
Another consequence of these rules is that where none of the items in a sequence contributes to the result of an expression, the processor is not obliged to evaluate any part of the sequence. Again, however, the processor cannot dispense with a required cardinality check: if an empty sequence is not permitted in the relevant context, then the processor must ensure that the operand is not an empty sequence.
Examples:
If an implementation can find (for example, by using an index)
that at least one item returned by $expr1
in the
following example has the value 47
, it is allowed to
return true
as the result of the some
expression, without searching for another item returned by
$expr1
that would raise an error if it were
evaluated.
some $x in $expr1 satisfies $x = 47
In the following example, if an implementation can find (for
example, by using an index) the product
element-nodes
that have an id
child with the value 47
,
it is allowed to return these nodes as the result of the path expression,
without searching for another product
node that would
raise an error because it has an id
child whose value
is not an integer.
//product[id = 47]
For a variety of reasons, including optimization, implementations may rewrite expressions into a different form. There are a number of rules that limit the extent of this freedom:
Other than the raising or not raising of errors, the result of evaluating a rewritten expression must conform to the semantics defined in this specification for the original expression.
Note:
This allows an implementation to return a result in cases where the original expression would have raised an error, or to raise an error in cases where the original expression would have returned a result. The main cases where this is likely to arise in practice are (a) where a rewrite changes the order of evaluation, such that a subexpression causing an error is evaluated when the expression is written one way and is not evaluated when the expression is written a different way, and (b) where intermediate results of the evaluation cause overflow or other out-of-range conditions.
Note:
This rule does not mean that the result of the expression will always be the same in non-error cases as if it had not been rewritten, because there are many cases where the result of an expression is to some degree implementation-dependent or implementation-defined.
Conditional and typeswitch expressions must not raise a dynamic
error in respect of subexpressions occurring in a branch that is
not selected, and must not return the value delivered by a branch
unless that branch is selected. Thus, the following example must
not raise a dynamic error if the document abc.xml
does
not exist:
if (doc-available('abc.xml')) then doc('abc.xml') else ()
As stated earlier, an expression must not be rewritten to
dispense with a required cardinality check: for example,
string-length(//title)
must raise an error if the
document contains more than one title element.
Expressions must not be rewritten in such a way as to create or remove static errors. The static errors in this specification are defined for the original expression, and must be preserved if the expression is rewritten.
Expression rewrite is illustrated by the following examples.
Consider the expression //part[color eq "Red"]
. An
implementation might choose to rewrite this expression as
//part[color = "Red"][color eq "Red"]
. The
implementation might then process the expression as follows: First
process the "=
" predicate by probing an index on parts
by color to quickly find all the parts that have a Red color; then
process the "eq
" predicate by checking each of these
parts to make sure it has only a single color. The result would be
as follows:
Parts that have exactly one color that is Red are returned.
If some part has color Red together with some other color, an error is raised.
The existence of some part that has no color Red but has multiple non-Red colors does not trigger an error.
The expression in the following example cannot raise a casting error if it is evaluated exactly as written (i.e., left to right). Since neither predicate depends on the context position, an implementation might choose to reorder the predicates to achieve better performance (for example, by taking advantage of an index). This reordering could cause the expression to raise an error.
$N[@x castable as xs:date][xs:date(@x) gt xs:date("2000-01-01")]
To avoid unexpected errors caused by expression rewrite, tests
that are designed to prevent dynamic errors should be expressed
using conditional or
typeswitch
expressions. For example, the above
expression can be written as follows:
$N[if (@x castable as xs:date) then xs:date(@x) gt xs:date("2000-01-01") else false()]
This section explains some concepts that are important to the processing of XQuery 3.0 expressions.
An ordering called document order is defined among all the nodes accessible during processing of a given query, which may consist of one or more trees (documents or fragments). Document order is defined in [XQuery and XPath Data Model (XDM) 3.0], and its definition is repeated here for convenience. [Definition: The node ordering that is the reverse of document order is called reverse document order.]
Document order is a total ordering, although the relative order of some nodes is implementation-dependent. [Definition: Informally, document order is the order in which nodes appear in the XML serialization of a document.] [Definition: Document order is stable, which means that the relative order of two nodes will not change during the processing of a given query, even if this order is implementation-dependent.]
Within a tree, document order satisfies the following constraints:
The root node is the first node.
Every node occurs before all of its children and descendants.
Attribute nodes immediately follow the element node with which they are associated. The relative order of attribute nodes is stable but implementation-dependent.
The relative order of siblings is the order in which they occur
in the children
property of their parent node.
Children and descendants occur before following siblings.
The relative order of nodes in distinct trees is stable but implementation-dependent, subject to the following constraint: If any node in a given tree T1 is before any node in a different tree T2, then all nodes in tree T1 are before all nodes in tree T2.
The semantics of some XQuery 3.0 operators depend on a process
called atomization. Atomization is applied to a
value when the value is used in a context in which a sequence of
atomic values is required. The result of atomization is either a
sequence of atomic values or a type error [err:FOTY0012]. [Definition: Atomization of a sequence is
defined as the result of invoking the fn:data
function
on the sequence, as defined in [XQuery and XPath Functions and Operators
3.0].]
The semantics of fn:data
are repeated here for
convenience. The result of fn:data
is the sequence of
atomic values produced by applying the following rules to each item
in the input sequence:
If the item is an atomic value, it is returned.
If the item is a node, its typed value is returned ([err:FOTY0012] is raised if the node has no typed value.)
If the item is a function itemDM30 [err:FOTY0012] is raised.
Atomization is used in processing the following types of expressions:
Arithmetic expressions
Comparison expressions
Function calls and returns
Cast expressions
Constructor expressions for various kinds of nodes
order by
clauses in FLWOR expressions
group by
clauses in FLWOR expressions
Switch expressions
Under certain circumstances (listed below), it is necessary to
find the effective boolean value of a value. [Definition: The
effective boolean value of a value is defined as the result
of applying the fn:boolean
function to the value, as
defined in [XQuery and XPath
Functions and Operators 3.0].]
The dynamic semantics of fn:boolean
are repeated
here for convenience:
If its operand is an empty sequence, fn:boolean
returns false
.
If its operand is a sequence whose first item is a node,
fn:boolean
returns true
.
If its operand is a singleton value of type xs:boolean
or derived from xs:boolean
, fn:boolean
returns the value of its operand unchanged.
If its operand is a singleton value of type xs:string
,
xs:anyURI
, xs:untypedAtomic
, or a type
derived from one of these, fn:boolean
returns
false
if the operand value has zero length; otherwise
it returns true
.
If its operand is a singleton value of any numeric type or derived from a numeric type,
fn:boolean
returns false
if the operand
value is NaN
or is numerically equal to zero;
otherwise it returns true
.
In all other cases, fn:boolean
raises a type error
[err:FORG0006].
Note:
The effective
boolean value of a sequence that contains at least one node and
at least one atomic value may be nondeterministic in regions of a
query where ordering mode is
unordered
.
The effective boolean value of a sequence is computed implicitly during processing of the following types of expressions:
Logical expressions (and
, or
)
The fn:not
function
The where
clause of a FLWOR expression
Certain types of predicates, such as a[b]
Conditional expressions (if
)
Quantified expressions (some
,
every
)
WindowStartCondition and
WindowEndCondition
in window
clauses.
Note:
The definition of effective boolean value is not used when
casting a value to the type xs:boolean
, for example in
a cast
expression or when passing a value to a
function whose expected parameter is of type
xs:boolean
.
XQuery 3.0 has a set of functions that provide access to input data. These functions are of particular importance because they provide a way in which an expression can reference a document or a collection of documents. The input functions are described informally here; they are defined in [XQuery and XPath Functions and Operators 3.0].
An expression can access input data either by calling one of the input functions or by referencing some part of the dynamic context that is initialized by the external environment, such as a variable or context item.
The input functions supported by XQuery 3.0 are as follows:
The fn:doc
function takes a string containing a
URI. If that URI is associated with a document in available
documents, fn:doc
returns a document node whose
content is the data
model representation of the given document; otherwise it raises
a dynamic
error.
The fn:unparsed-text
function takes a string
containing a URI, which must identify a resource that can be read
as text; otherwise it raises a dynamic error.
The fn:environment-variable
and
fn:available-environment-variables
identify
environment variables that are available in the dynamic
context.
The fn:collection
function with one argument takes
a string containing a URI. If that URI is associated with a
collection in available collections,
fn:collection
returns the data model representation of
that collection; otherwise it raises a dynamic error. A collection may be any
sequence of nodes. For example, the expression
fn:collection("http://example.org")//customer
identifies all the customer
elements that are
descendants of nodes found in the collection whose URI is
http://example.org
.
The fn:collection
function with zero arguments
returns the default collection, an implementation-dependent
sequence of nodes.
The fn:uri-collection
function returns a sequence
of xs:anyURI
values representing the document URIs of
the documents in a collection.
These input functions are all specified in [XQuery and XPath Functions and Operators 3.0], which specifies error conditions and other details not described here.
In certain places in the grammar, a statically known valid URI is required. These places are denoted by the grammatical symbol URILiteral. For example, URILiterals are used to specify namespaces and collations, both of which must be statically known.
[191] | URILiteral |
::= | StringLiteral |
Syntactically, a URILiteral is identical to a StringLiteral: a sequence of zero
or more characters enclosed in single or double quotes. However, an
implementation may raise a static error [err:XQST0046] if the value of a URILiteral is of
nonzero length and is not in the lexical space of
xs:anyURI
.
As in a string literal, any predefined entity reference
(such as &
), character reference (such as
•
), or EscapeQuot or EscapeApos (for example,
""
) is replaced by its appropriate expansion. Certain
characters, notably the ampersand, can only be represented using a
predefined entity reference
or a character reference.
Note:
The xs:anyURI
type is designed to anticipate the
introduction of Internationalized Resource Identifiers (IRI's) as
defined in [RFC3987].
The following is an example of a valid URILiteral:
"http://www.w3.org/2005/xpath-functions/collation/codepoint"
[Definition: To resolve a relative URI
$rel
against a base URI $base
is to
expand it to an absolute URI, as if by calling the function
fn:resolve-uri($rel, $base)
.] During query analysis,
the base URI is the Static Base URI. During dynamic evaluation, the
base URI used to resolve a relative URI depends on the semantics of
the expression.
The URILiteral is subjected to whitespace normalization as
defined for the xs:anyURI
type in [XML Schema 1.0] or [XML
Schema 1.1]: this means that leading and trailing whitespace is
removed, and any other sequence of whitespace characters is
replaced by a single space (#x20) character. Whitespace normalization is done after the expansion of
character references, so writing a
newline (for example) as 

does not prevent
its being normalized to a space character.
The URILiteral is not automatically subjected to percent-encoding or decoding as defined in [RFC3986]. Any process that attempts to resolve the URI against a base URI, or to dereference the URI, may however apply percent-encoding or decoding as defined in the relevant RFCs.
The type system of XQuery 3.0 is based on [XML Schema 1.0] or [XML Schema 1.1].
[Definition: A sequence type is a type that can be expressed using the SequenceType syntax. Sequence types are used whenever it is necessary to refer to a type in an XQuery 3.0 expression. The term sequence type suggests that this syntax is used to describe the type of an XQuery 3.0 value, which is always a sequence.]
[Definition: A schema type is a type that
is (or could be) defined using the facilities of [XML Schema 1.0] or [XML
Schema 1.1] (including the built-in types of [XML Schema 1.0] or [XML
Schema 1.1]).] A schema type can be used as a type annotation
on an element or attribute node (unless it is a non-instantiable
type such as xs:NOTATION
or
xs:anyAtomicType
, in which case its derived types can
be so used). Every schema type is either a complex type or a
simple type; simple types are further subdivided into
list types, union types, and atomic types (see
[XML Schema 1.0] or [XML Schema 1.1] for definitions and
explanations of these terms.)
Atomic types represent the intersection between the categories
of sequence
type and schema
type. An atomic type, such as xs:integer
or
my:hatsize
, is both a sequence type and a schema type.
The schema types defined in [XQuery and XPath Data Model (XDM) 3.0] are summarized below.
The in-scope schema types in the static context are
initialized with certain predefined schema types, including the
built-in schema types in the namespace
http://www.w3.org/2001/XMLSchema
, which has the
predefined namespace prefix xs
. The schema types in
this namespace are defined in [XML Schema
1.0] or [XML Schema 1.1] and
augmented by additional types defined in [XQuery and XPath Data Model (XDM) 3.0].
Element and attribute declarations in the xs
namespace
are not implicitly included in the static context. The schema types
defined in [XQuery and XPath Data
Model (XDM) 3.0] are summarized below.
[Definition: xs:untyped
is used as the
type
annotation of an element node that has not been validated, or
has been validated in skip
mode.] No predefined schema
types are derived from xs:untyped
.
[Definition: xs:untypedAtomic
is
an atomic type that is used to denote untyped atomic data, such as
text that has not been assigned a more specific type.] An attribute
that has been validated in skip
mode is represented in
the data model by an
attribute node with the type annotation
xs:untypedAtomic
. No predefined schema types are
derived from xs:untypedAtomic
.
[Definition:
xs:dayTimeDuration
is derived by restriction from
xs:duration
. The lexical representation of
xs:dayTimeDuration
is restricted to contain only day,
hour, minute, and second components.]
[Definition:
xs:yearMonthDuration
is derived by restriction from
xs:duration
. The lexical representation of
xs:yearMonthDuration
is restricted to contain only
year and month components.]
[Definition: xs:anyAtomicType
is
an atomic type that includes all atomic values (and no values that
are not atomic). Its base type is xs:anySimpleType
from which all simple types, including atomic, list, and union
types, are derived. All primitive atomic types, such as
xs:decimal
and xs:string
, have
xs:anyAtomicType
as their base type.]
Note:
xs:anyAtomicType
will not appear as the type of an
actual value in an XDM instance.
The relationships among the schema types in the xs
namespace are illustrated in Figure 2. A more complete description
of the XQuery 3.0 type hierarchy can be found in [XQuery and XPath Functions and Operators
3.0].
Figure 2: Hierarchy of Schema Types used in XQuery 3.0.
[Definition: The
namespace-sensitive types are xs:QName
,
xs:NOTATION
, types derived by restriction from
xs:QName
or xs:NOTATION
, list types that
have a namespace-sensitive item type, and union types with a
namespace-sensitive type in their transitive membership.]
It is not possible to preserve the type of a namespace-sensitive value without also preserving the namespace binding that defines the meaning of each namespace prefix used in the value. Therefore, XQuery 3.0 defines some error conditions that occur only with namespace-sensitive values. For instance, copying nodes with namespace-sensitive types can raise such an error if done using a mode that prohibits copying namespace bindings (see 3.8.1.3 Content), and casts to namespace-sensitive types raise an error if the input expression, when evaluated, contains a node (see 3.15.3 Cast).
Every node has a typed value and a string value.
[Definition: The typed value of a node is a
sequence of atomic values and can be extracted by applying the
fn:data
function to the node.] [Definition: The string value of a node is
a string and can be extracted by applying the
fn:string
function to the node.] Definitions of
fn:data
and fn:string
can be found in
[XQuery and XPath Functions and
Operators 3.0].
An implementation may store both the typed value and the string value of a node,
or it may store only one of these and derive the other as needed.
The string value of a node must be a valid lexical representation
of the typed value of the node, but the node is not required to
preserve the string representation from the original source
document. For example, if the typed value of a node is the
xs:integer
value 30
, its string value
might be "30
" or "0030
".
The typed value, string value, and type annotation of a node are closely related, and are defined by rules found in the following locations:
If the node was created by mapping from an Infoset or PSVI, see rules in [XQuery and XPath Data Model (XDM) 3.0].
If the node was created by an XQuery node constructor, see rules in 3.8.1 Direct Element Constructors, 3.8.3.1 Computed Element Constructors, or 3.8.3.2 Computed Attribute Constructors.
If the node was created by a validate
expression,
see rules in 3.16 Validate
Expressions.
As a convenience to the reader, the relationship between typed value and string value for various kinds of nodes is summarized and illustrated by examples below.
For text and document nodes, the typed value of the node is the
same as its string value, as an instance of the type
xs:untypedAtomic
. The string value of a document node
is formed by concatenating the string values of all its descendant
text nodes, in document order.
The typed value of a comment or processing instruction node is
the same as its string value. It is an instance of the type
xs:string
.
The typed value of an attribute node with the type annotation
xs:anySimpleType
or xs:untypedAtomic
is
the same as its string value, as an instance of
xs:untypedAtomic
. The typed value of an attribute node
with any other type annotation is derived from its string value and
type annotation using the lexical-to-value-space mapping defined in
[XML Schema 1.0] or [XML Schema 1.1] Part 2 for the relevant
type.
Example: A1 is an attribute having string value
"3.14E-2"
and type annotation xs:double
.
The typed value of A1 is the xs:double
value whose
lexical representation is 3.14E-2
.
Example: A2 is an attribute with type annotation
xs:IDREFS
, which is a list datatype whose item type is
the atomic datatype xs:IDREF
. Its string value is
"bar baz faz
". The typed value of A2 is a sequence of
three atomic values ("bar
", "baz
",
"faz
"), each of type xs:IDREF
. The typed
value of a node is never treated as an instance of a named list
type. Instead, if the type annotation of a node is a list type
(such as xs:IDREFS
), its typed value is treated as a
sequence of the atomic type from which it is derived (such as
xs:IDREF
).
For an element node, the relationship between typed value and string value depends on the node's type annotation, as follows:
If the type annotation is xs:untyped
or
xs:anySimpleType
or denotes a complex type with mixed
content (including xs:anyType
), then the typed value
of the node is equal to its string value, as an instance of
xs:untypedAtomic
. However, if the nilled
property of the node is true
, then its typed value is
the empty sequence.
Example: E1 is an element node having type annotation
xs:untyped
and string value "1999-05-31
".
The typed value of E1 is "1999-05-31
", as an instance
of xs:untypedAtomic
.
Example: E2 is an element node with the type annotation
formula
, which is a complex type with mixed content.
The content of E2 consists of the character "H
", a
child element named subscript
with string value
"2
", and the character "O
". The typed
value of E2 is "H2O
" as an instance of
xs:untypedAtomic
.
If the type annotation denotes a simple type or a complex type
with simple content, then the typed value of the node is derived
from its string value and its type annotation in a way that is
consistent with schema validation. However, if the
nilled
property of the node is true
, then
its typed value is the empty sequence.
Example: E3 is an element node with the type annotation
cost
, which is a complex type that has several
attributes and a simple content type of xs:decimal
.
The string value of E3 is "74.95
". The typed value of
E3 is 74.95
, as an instance of
xs:decimal
.
Example: E4 is an element node with the type annotation
hatsizelist
, which is a simple type derived from the
atomic type hatsize
, which in turn is derived from
xs:integer
. The string value of E4 is "7 8
9
". The typed value of E4 is a sequence of three values
(7
, 8
, 9
), each of type
hatsize
.
Example: E5 is an element node with the type annotation
my:integer-or-string
which is a union type with member
types xs:integer
and xs:string
. The
string value of E5 is "47
". The typed value of E5 is
47
as an xs:integer
, since
xs:integer
is the member type that validated the
content of E5. In general, when the type annotation of a node is a
union type, the typed value of the node will be an instance of one
of the member types of the union.
Note:
If an implementation stores only the string value of a node, and the type annotation of the node is a union type, the implementation must be able to deliver the typed value of the node as an instance of the appropriate member type.
If the type annotation denotes a complex type with empty content, then the typed value of the node is the empty sequence and its string value is the zero-length string.
If the type annotation denotes a complex type with element-only
content, then the typed value of the node is undefined. The
fn:data
function raises a type error [err:FOTY0012] when applied to such
a node. The string value of such a node is equal to the
concatenated string values of all its text node descendants, in
document order.
Example: E6 is an element node with the type annotation
weather
, which is a complex type whose content type
specifies element-only
. E6 has two child elements
named temperature
and precipitation
. The
typed value of E6 is undefined, and the fn:data
function applied to E6 raises an error.
Whenever it is necessary to refer to a type in an XQuery 3.0 expression, the SequenceType syntax is used.
[165] | SequenceType |
::= | ("empty-sequence" "(" ")") |
[167] | ItemType |
::= | KindTest | ("item"
"(" ")") | FunctionTest |
AtomicOrUnionType |
ParenthesizedItemType |
[166] | OccurrenceIndicator |
::= | "?" | "*" | "+" |
[168] | AtomicOrUnionType |
::= | EQName |
[169] | KindTest |
::= | DocumentTest |
[171] | DocumentTest |
::= | "document-node" "(" (ElementTest | SchemaElementTest)?
")" |
[180] | ElementTest |
::= | "element" "(" (ElementNameOrWildcard
("," TypeName "?"?)?)?
")" |
[182] | SchemaElementTest |
::= | "schema-element" "(" ElementDeclaration
")" |
[183] | ElementDeclaration |
::= | ElementName |
[176] | AttributeTest |
::= | "attribute" "(" (AttribNameOrWildcard (","
TypeName)?)? ")" |
[178] | SchemaAttributeTest |
::= | "schema-attribute" "(" AttributeDeclaration
")" |
[179] | AttributeDeclaration |
::= | AttributeName |
[181] | ElementNameOrWildcard |
::= | ElementName |
"*" |
[185] | ElementName |
::= | EQName |
[177] | AttribNameOrWildcard |
::= | AttributeName |
"*" |
[184] | AttributeName |
::= | EQName |
[186] | TypeName |
::= | EQName |
[175] | PITest |
::= | "processing-instruction" "(" (NCName | StringLiteral)? ")" |
[173] | CommentTest |
::= | "comment" "(" ")" |
[174] | NamespaceNodeTest |
::= | "namespace-node" "(" ")" |
[172] | TextTest |
::= | "text" "(" ")" |
[170] | AnyKindTest |
::= | "node" "(" ")" |
[187] | FunctionTest |
::= | Annotation*
(AnyFunctionTest |
[188] | AnyFunctionTest |
::= | "function" "(" "*" ")" |
[189] | TypedFunctionTest |
::= | "function" "(" (SequenceType ("," SequenceType)*)? ")" "as" SequenceType |
[190] | ParenthesizedItemType |
::= | "(" ItemType
")" |
With the exception of the special type
empty-sequence()
, a sequence type consists of an item
type that constrains the type of each item in the sequence, and
a cardinality that constrains the number of items in the
sequence. Apart from the item type item()
, which
permits any kind of item, item types divide into node types
(such as element()
), atomic types (such as
xs:integer
) and function types (such as function() as
item()*).
Item types representing element and attribute nodes may specify
the required type annotations of those nodes, in the
form of a schema
type. Thus the item type element(*, us:address)
denotes any element node whose type annotation is (or is derived
from) the schema type named us:address
.
Any occurrence of '+' and '*', as well as '?' immediately following a sequence type is assumed to be an occurrence indicator, which binds to the last ItemType in the SequenceType, as described in occurrence-indicators constraint.
Here are some examples of sequence types that might be used in XQuery 3.0:
xs:date
refers to the built-in atomic schema type
named xs:date
attribute()?
refers to an optional attribute
node
element()
refers to any element node
element(po:shipto, po:address)
refers to an element
node that has the name po:shipto
and has the type
annotation po:address
(or a schema type derived from
po:address
)
element(*, po:address)
refers to an element node of
any name that has the type annotation po:address
(or a
type derived from po:address
)
element(customer)
refers to an element node named
customer
with any type annotation
schema-element(customer)
refers to an element node
whose name is customer
(or is in the substitution
group headed by customer
) and whose type annotation
matches the schema type declared for a customer
element in the in-scope element declarations
node()*
refers to a sequence of zero or more nodes
of any kind
item()+
refers to a sequence of one or more
items
function(*)
refers to any function
itemDM30, regardless of arity or
type
function(node()) as xs:string*
refers to a function
itemDM30 that takes a single argument
whose value is a single node, and returns a sequence of zero or
more xs:string values
(function(node()) as xs:string)*
refers to a
sequence of zero or more function
itemsDM30, each of which takes a
single argument whose value is a single node, and returns as its
result a single xs:string value
[Definition: During evaluation of an
expression, it is sometimes necessary to determine whether a value
with a known dynamic type "matches" an expected sequence type. This
process is known as SequenceType matching.] For example, an
instance of
expression returns true
if
the dynamic
type of a given value matches a given sequence type, or false
if it does not.
Lexical QNames
appearing in a sequence type have their prefixes expanded
to namespace URIs by means of the statically known namespaces and (where
applicable) the default element/type namespace or
default
function namespace. Equality of QNames is defined by the
eq
operator.
The rules for SequenceType matching compare the dynamic type of a value with an expected sequence type.
An XQuery 3.0 implementation must be able to determine relationships among the types in type annotations in an XDM instance and the types in the in-scope schema definitions (ISSD). An XQuery 3.0 implementation must be able to determine relationships among the types in ISSDs used in different modules of the same query.
[Definition: The use of a value
whose dynamic
type is derived from an expected type is known as subtype
substitution.] Subtype substitution does not change the actual
type of a value. For example, if an xs:integer
value
is used where an xs:decimal
value is expected, the
value retains its type as xs:integer
.
The definition of SequenceType matching relies on a
pseudo-function named derives-from(
AT,
ET )
, which takes an actual simple or complex
schema type AT and an expected simple or complex schema
type ET, and either returns a boolean value or raises a
type error
[err:XPTY0004].
This function is defined as follows:
derives-from(
AT, ET
)
raises a type error [err:XPTY0004] if ET is not present in
the in-scope schema definitions (ISSD).
derives-from(
AT, ET
)
returns true
if AT is derived
from ET by restriction or extension, or if ET is
a union type of which AT is a member type.
Formally, it returns true
if AT is validly
derived from ET given the empty set, as defined in
[XML Schema 1.0] or [XML Schema 1.1] Part 1 constraints Type
Derivation OK (Complex) (if AT is a complex type), or Type
Derivation OK (Simple) (if AT is a simple type). The
phrase "given the empty set" is used because the rules in the XML
Schema specification are parameterized: the parameter is a list of
the kinds of derivation that are not allowed, and in this case the
list is always empty.
Note:
The current (second) edition of XML Schema 1.0 contains an error in respect of the substitutability of a union type by one of its members: it fails to recognize that this is unsafe if the union is derived by restriction from another union. This problem is fixed in the current working draft of XML Schema 1.1, and implementers are advised to adopt the solution given there. It is likely that this specification will be updated to refer normatively to XML Schema 1.1 when that specification reaches Recommendation status.
Otherwise, derives-from(
AT, ET
)
returns false
The rules for SequenceType matching are given below, with examples (the examples are for purposes of illustration, and do not cover all possible cases).
The sequence
type empty-sequence()
matches a value that is the
empty sequence.
An ItemType with no OccurrenceIndicator matches any value that contains exactly one item if the ItemType matches that item (see 2.5.5.2 Matching an ItemType and an Item).
An ItemType with an OccurrenceIndicator matches a value if the number of items in the value matches the OccurrenceIndicator and the ItemType matches each of the items in the value.
An OccurrenceIndicator specifies the number of items in a sequence, as follows:
?
matches zero or one items
*
matches zero or more items
+
matches one or more items
As a consequence of these rules, any sequence type whose OccurrenceIndicator is
*
or ?
matches a value that is an empty
sequence.
An ItemType consisting
simply of an EQName is interpreted as an AtomicOrUnionType. The
expected type AtomicOrUnionType matches an atomic value
whose actual type is AT if derives-from(
AT, AtomicOrUnionType )
is
true
.
Note:
derives-from()
is defined for both union types and
atomic types.
The name of an AtomicOrUnionType has its prefix expanded to a namespace URI by means of the statically known namespaces, or if unprefixed, the default element/type namespace. If the expanded QName of an AtomicOrUnionType is not defined as an atomic type or a union type in the in-scope schema types, a static error is raised [err:XPST0051].
Example: The ItemType
xs:decimal
matches any value of type
xs:decimal
. It also matches any value of type
shoesize
, if shoesize
is an atomic type
derived by restriction from xs:decimal
.
Example: Suppose ItemType
dress-size
is a union type that allows either
xs:decimal
values for numeric sizes (e.g. 4, 6, 10,
12), or one of an enumerated set of xs:strings
(e.g.
"small", "medium", "large"). The ItemType dress-size
matches any of these values.
Note:
The names of non-atomic types such as xs:IDREFS
are
not accepted in this context, but can often be replaced by an
atomic type with an occurrence indicator, such as
xs:IDREF+
.
item()
matches any single item.
Example: item()
matches the atomic value
1
, the element <a/>
, or the
function item fn:concat#3
.
node()
matches any node.
text()
matches any text node.
processing-instruction()
matches any
processing-instruction node.
processing-instruction(
N )
matches any processing-instruction node whose PITarget is equal to
fn:normalize-space(N)
. If
fn:normalize-space(N)
is not in the lexical space of
NCName, a type error is raised [err:XPTY0004]
Example: processing-instruction(xml-stylesheet)
matches any processing instruction whose PITarget is
xml-stylesheet
.
For backward compatibility with XPath 1.0, the PITarget of a
processing instruction may also be expressed as a string literal,
as in this example:
processing-instruction("xml-stylesheet")
.
If the specified PITarget is not a syntactically valid NCName, a type error is raised [err:XPTY0004].
comment()
matches any comment node.
namespace-node()
matches any namespace node.
document-node()
matches any document node.
document-node(
E )
matches
any document node that contains exactly one element node,
optionally accompanied by one or more comment and processing
instruction nodes, if E is an ElementTest or SchemaElementTest that
matches the element node (see 2.5.5.3
Element Test and 2.5.5.4 Schema Element
Test).
Example: document-node(element(book))
matches a
document node containing exactly one element node that is matched
by the ElementTest element(book)
.
A ParenthesizedItemType matches an item if and only if the item matches the ItemType that is in parentheses.
An ItemType that is an ElementTest, SchemaElementTest, AttributeTest, SchemaAttributeTest, or FunctionTest matches an item as described in the following sections.
[180] | ElementTest |
::= | "element" "(" (ElementNameOrWildcard
("," TypeName "?"?)?)?
")" |
[181] | ElementNameOrWildcard |
::= | ElementName |
"*" |
[185] | ElementName |
::= | EQName |
[186] | TypeName |
::= | EQName |
An ElementTest is used to match an element node by its name and/or type annotation.
The ElementName and TypeName of an ElementTest have their prefixes expanded to namespace URIs by means of the statically known namespaces, or if unprefixed, the default element/type namespace. The ElementName need not be present in the in-scope element declarations, but the TypeName must be present in the in-scope schema types [err:XPST0008]. Note that substitution groups do not affect the semantics of ElementTest.
An ElementTest may take any of the following forms:
element()
and element(*)
match any
single element node, regardless of its name or type annotation.
element(
ElementName )
matches
any element node whose name is ElementName, regardless of its type
annotation or nilled
property.
Example: element(person)
matches any element node
whose name is person
.
element(
ElementName ,
TypeName )
matches an
element node whose name is ElementName if
derives-from(
AT, TypeName )
is
true
, where AT is the type annotation of the
element node, and the nilled
property of the node is
false
.
Example: element(person, surgeon)
matches a
non-nilled element node whose name is person
and whose
type annotation is surgeon
(or is derived from
surgeon
).
element(
ElementName, TypeName ?)
matches an
element node whose name is ElementName if
derives-from(
AT, TypeName )
is
true
, where AT is the type annotation of the
element node. The nilled
property of the node may be
either true
or false
.
Example: element(person, surgeon?)
matches a nilled
or non-nilled element node whose name is person
and
whose type annotation is surgeon
(or is derived from
surgeon
).
element(*,
TypeName )
matches an
element node regardless of its name, if derives-from(
AT, TypeName
)
is true
, where AT is the type
annotation of the element node, and the nilled
property of the node is false
.
Example: element(*, surgeon)
matches any non-nilled
element node whose type annotation is surgeon
(or is
derived from surgeon
), regardless of its name.
element(*,
TypeName ?)
matches an
element node regardless of its name, if derives-from(
AT, TypeName
)
is true
, where AT is the type
annotation of the element node. The nilled
property of
the node may be either true
or false
.
Example: element(*, surgeon?)
matches any nilled or
non-nilled element node whose type annotation is
surgeon
(or is derived from surgeon
),
regardless of its name.
[182] | SchemaElementTest |
::= | "schema-element" "(" ElementDeclaration
")" |
[183] | ElementDeclaration |
::= | ElementName |
[185] | ElementName |
::= | EQName |
A SchemaElementTest matches an element node against a corresponding element declaration found in the in-scope element declarations.
The ElementName of a SchemaElementTest has its prefixes expanded to a namespace URI by means of the statically known namespaces, or if unprefixed, the default element/type namespace. If the ElementName specified in the SchemaElementTest is not found in the in-scope element declarations, a static error is raised [err:XPST0008].
A SchemaElementTest matches a candidate element node if all of the following conditions are satisfied:
The name of the candidate node matches the specified ElementName, or it matches the name of an element in a substitution group headed by an element named ElementName and the substituted element is not abstract. Call this element the substituted element.
derives-from(
AT, ET )
is
true
, where AT is the type annotation of the
candidate node and ET is the schema type declared for
the substituted element in the in-scope
element declarations.
If the the substituted element is not
nillable
, then the nilled
property of the
candidate node is false
.
Example: The SchemaElementTest
schema-element(customer)
matches a candidate element
node if customer
is a top-level element declaration in
the in-scope element declarations, the name of the
candidate node is customer
or is in a substitution
group headed by customer
, the type annotation of
the candidate node is the same as or derived from the schema type
declared for the customer
element, and either the
candidate node is not nilled
or customer
is declared to be nillable
.
[176] | AttributeTest |
::= | "attribute" "(" (AttribNameOrWildcard (","
TypeName)?)? ")" |
[177] | AttribNameOrWildcard |
::= | AttributeName |
"*" |
[184] | AttributeName |
::= | EQName |
[186] | TypeName |
::= | EQName |
An AttributeTest is used to match an attribute node by its name and/or type annotation.
The AttributeName and TypeName of an AttributeTest have their prefixes expanded to namespace URIs by means of the statically known namespaces. If unprefixed, the AttributeName is in no namespace, but an unprefixed TypeName is in the default element/type namespace. The AttributeName need not be present in the in-scope attribute declarations, but the TypeName must be present in the in-scope schema types [err:XPST0008].
An AttributeTest may take any of the following forms:
attribute()
and attribute(*)
match any
single attribute node, regardless of its name or type
annotation.
attribute(
AttributeName )
matches any attribute node whose name is AttributeName, regardless of its
type annotation.
Example: attribute(price)
matches any attribute
node whose name is price
.
attribute(
AttributeName, TypeName )
matches an
attribute node whose name is AttributeName if
derives-from(
AT, TypeName )
is
true
, where AT is the type annotation of the
attribute node.
Example: attribute(price, currency)
matches an
attribute node whose name is price
and whose type
annotation is currency
(or is derived from
currency
).
attribute(*,
TypeName )
matches an
attribute node regardless of its name, if
derives-from(
AT, TypeName )
is
true
, where AT is the type annotation of the
attribute node.
Example: attribute(*, currency)
matches any
attribute node whose type annotation is currency
(or
is derived from currency
), regardless of its name.
[178] | SchemaAttributeTest |
::= | "schema-attribute" "(" AttributeDeclaration
")" |
[179] | AttributeDeclaration |
::= | AttributeName |
[184] | AttributeName |
::= | EQName |
A SchemaAttributeTest matches an attribute node against a corresponding attribute declaration found in the in-scope attribute declarations.
The AttributeName of a SchemaAttributeTest has its prefixes expanded to a namespace URI by means of the statically known namespaces. If unprefixed, an AttributeName is in no namespace. If the AttributeName specified in the SchemaAttributeTest is not found in the in-scope attribute declarations, a static error is raised [err:XPST0008].
A SchemaAttributeTest matches a candidate attribute node if both of the following conditions are satisfied:
The name of the candidate node matches the specified AttributeName.
derives-from(
AT, ET )
is
true
, where AT is the type annotation of the
candidate node and ET is the schema type declared for
attribute AttributeName
in the in-scope attribute declarations.
Example: The SchemaAttributeTest
schema-attribute(color)
matches a candidate attribute
node if color
is a top-level attribute declaration in
the in-scope attribute declarations, the name of the
candidate node is color
, and the type annotation of
the candidate node is the same as or derived from the schema type
declared for the color
attribute.
[187] | FunctionTest |
::= | Annotation*
(AnyFunctionTest |
[188] | AnyFunctionTest |
::= | "function" "(" "*" ")" |
[189] | TypedFunctionTest |
::= | "function" "(" (SequenceType ("," SequenceType)*)? ")" "as" SequenceType |
A FunctionTest matches a function itemDM30, potentially also checking its function signature and annotations (see 4.15 Annotations).
[Definition: If an annotation is present in a FunctionTest, it is called an annotation assertion.] Annotation assertions further restrict the set of function items that are matched by a FunctionTest.
Implementations MAY define further annotation assertions, whose behaviour is implementation-defined. Implementations MAY provide a way for users to create their own annotation assertions. Implementations MUST NOT define annotation assertions in the following reserved namespaces; it is an error for users to create annotation assertions in the following reserved namespaces [err:XQST0045]:
http://www.w3.org/XML/1998/namespace
http://www.w3.org/2001/XMLSchema
http://www.w3.org/2001/XMLSchema-instance
http://www.w3.org/2005/xpath-functions
http://www.w3.org/2005/xpath-functions/math
Note:
There are no annotation assertions that correspond to the
%public
and %private
annotations.
Annotation assertions are not automatically defined as a side
effect of creating an annotation.
Note:
Other specifications in the XQuery family will also use
annotation assertions. For instance, in the XQuery Update Facility,
%fn:updating
matches function items with a
%fn:simple
or %fn:updating
annotation. In
the XQuery Scripting Extension, %fn:sequential
matches
function items with a %fn:simple
or
%fn:sequential
annotation, and %fn:simple
matches function items with a %fn:simple annotation
.
If no %fn:updating
or %fn:sequential
annotation assertion is present, this is the default matching
behaviour.
A FunctionTest may take any of the following forms:
function(*)
matches any function
itemDM30.
A TypedFunctionTest matches an item if it is a function itemDM30, and the function item's type signature (as defined in Section 2.8.1 Function Items DM30) is a subtype of the TypedFunctionTest.
Given two sequence types, it is possible to determine
if one is a subtype of the other. [Definition: A sequence type
A
is a subtype of a sequence type
B
if and only if, for every value V
, if
V
matches A
according to the rules of
SequenceType matching, then
V
also matches B
.] The subtype
relationship can be computed using the subtype(A, B)
,
subtype-itemtype(Ai, Bi)
,
subtype-assertions(AnnotationsA, AnnotationsB)
, and
derives-from(AT, ET)
judgements.
The judgement subtype(A, B)
determines if the
sequence type
A
is a subtype of the sequence type B
.
A
can either be empty-sequence()
or an
ItemType, Ai
,
possibly followed by an occurrence indicator. Similarly
B
can either be empty-sequence()
or an
ItemType, Bi
,
possibly followed by an occurrence indicator. The result of the
subtype(A, B)
judgement can be determined from the
table below, which makes use of the auxiliary judgement
subtype-itemtype(Ai, Bi)
defined in 2.5.6.2 The ItemType Subtype
Judgement.
Sequence type B |
||||||
---|---|---|---|---|---|---|
empty-sequence() |
Bi? |
Bi* |
Bi |
Bi+ |
||
Sequence type A |
empty-sequence() |
true | true | true | false | false |
Ai? |
false | subtype-itemtype(Ai, Bi) |
subtype-itemtype(Ai, Bi) |
false | false | |
Ai* |
false | false | subtype-itemtype(Ai, Bi) |
false | false | |
Ai |
false | subtype-itemtype(Ai, Bi) |
subtype-itemtype(Ai, Bi) |
subtype-itemtype(Ai, Bi) |
subtype-itemtype(Ai, Bi) |
|
Ai+ |
false | false | subtype-itemtype(Ai, Bi) |
false | subtype-itemtype(Ai, Bi) |
The judgement subtype-itemtype(Ai, Bi)
determines
if the ItemType
Ai
is a subtype of the ItemType Bi
.
Ai
is a subtype of Bi
if and only if at
least one of the following conditions applies:
Ai
and Bi
are AtomicOrUnionTypes, and
derives-from(Ai, Bi)
returns true
.
Bi
is item()
.
Bi
is node()
, and Ai
is a
KindTest.
Bi
is text()
and Ai
is
also text()
.
Bi
is comment()
and Ai
is
also comment()
.
Bi
is namespace-node()
and
Ai
is also namespace-node()
.
Bi
is processing-instruction()
and
Ai
is either processing-instruction()
or
processing-instruction(N)
for any name N..
Bi
is processing-instruction(Bn)
, and
Ai
is also
processing-instruction(Bn)
.
Bi
is document-node()
and
Ai
is either document-node()
or
document-node(E)
for any ElementTest E.
Bi
is document-node(Be)
and
Ai
is document-node(Ae)
, and
subtype-itemtype(Ae, Be)
.
Bi
is either element()
or
element(*)
, and Ai
is an ElementTest.
Bi
is either element(Bn)
or
element(Bn, xs:anyType)
, and Ai
is either
element(Bn)
, or element(Bn, T)
for any
type T.
Bi
is element(Bn, Bt)
, Ai
is element(Bn, At)
, and derives-from(At,
Bt)
returns true
.
Bi
is element(Bn, Bt?)
,
Ai
is either element(Bn, At)
, or
element(Bn, At?)
, and derives-from(At,
Bt)
returns true
.
Bi
is element(*, Bt)
, Ai
is either element(*, At)
, or element(N,
At)
for any name N, and derives-from(At, Bt)
returns true
.
Bi
is element(*, Bt?)
, Ai
is either element(*, At)
, element(*,
At?)
, element(N, At)
, or element(N,
At?)
for any name N, and derives-from(At, Bt)
returns true
.
Bi
is schema-element(Bn)
,
Ai
is schema-element(An)
, and either the
expanded
QName An
equals the expanded QName Bn
or the
element declaration named An
is in the substitution
group of the element declaration named Bn
.
Bi
is either attribute()
or
attribute(*)
, and Ai
is an AttributeTest.
Bi
is either attribute(Bn)
or
attribute(Bn, xs:anyType)
, and Ai
is
either attribute(Bn)
, or attribute(Bn, T)
for any type T.
Bi
is attribute(Bn, Bt)
,
Ai
is attribute(Bn, At)
, and
derives-from(At, Bt)
returns true
.
Bi
is attribute(*, Bt)
,
Ai
is either attribute(*, At)
, or
attribute(N, At)
for any name N, and
derives-from(At, Bt)
returns true
.
Bi
is schema-attribute(Bn)
and
Ai
is also schema-attribute(Bn)
.
Bi
is AnnotationsB function(*)
,
Ai
is a FunctionTest with annotations
AnnotationsA
, and
subtype-assertions(AnnotationsA, AnnotationsB)
.
Bi
is AnnotationsB function(Ba_1, Ba_2, ...
Ba_N) as Br
, Ai
is AnnotationsA
function(Aa_1, Aa_2, ... Aa_M) as Ar
, N
(arity
of Bi) equals M
(arity of Ai), subtype(Ar,
Br)
, for values of I
between 1 and
N
, subtype(Ba_I, Aa_I)
, and
subtype-assertions(AnnotationsA, AnnotationsB)
.
The judgement subtype-assertions(AnnotationsA,
AnnotationsB)
determines if AnnotationsA
is a
subtype of AnnotationsB
, where
AnnotationsA
and AnnotationsB
are
annotation lists from two FunctionTests. It is defined to ignore
annotation assertions in namespaces not understood by the XQuery
implementation. For assertions that are understood, their effect on
the result of subtype-assertions()
is implementation
defined.
The following examples are some possible ways to define
subtype-assertions()
for some implementation defined
assertions in the local
namespace:
AnnotationsA is %local:inline
, which has no
influence on the outcome of subtype-assertions()
.
AnnotationsA is %local:deterministic
and
AnnotationsB is %local:non-deterministic
. Since
deterministic functions are a subset of non-deterministic
functions, subtype-assertions()
is true.
AnnotationsA contains %local:non-deterministic
and
AnnotationsB is empty. If FunctionTests without the
%local:non-deterministic
annotation only match
deterministic functions, subtype-assertions()
must be
false.
[204] | Comment |
::= | "(:" (CommentContents | Comment)* ":)" |
[212] | CommentContents |
::= | (Char+ - (Char* ('(:' |
':)') Char*)) |
Comments may be used to provide informative annotation for a query, either in the Prolog or in the Query Body . Comments are lexical constructs only, and do not affect query processing.
Comments are strings, delimited by the symbols (:
and :)
. Comments may be nested.
A comment may be used anywhere ignorable whitespace is allowed (see A.2.4.1 Default Whitespace Handling).
The following is an example of a comment:
(: Houston, we have a problem :)
This section discusses each of the basic kinds of expression.
Each kind of expression has a name such as PathExpr
,
which is introduced on the left side of the grammar production that
defines the expression. Since XQuery 3.0 is a composable language,
each kind of expression is defined in terms of other expressions
whose operators have a higher precedence. In this way, the
precedence of operators is represented explicitly in the
grammar.
The order in which expressions are discussed in this document does not reflect the order of operator precedence. In general, this document introduces the simplest kinds of expressions first, followed by more complex expressions. For the complete grammar, see Appendix [A XQuery 3.0 Grammar].
[Definition: A query consists of one or more modules.] If a query is executable, one of its modules has a Query Body containing an expression whose value is the result of the query. An expression is represented in the XQuery grammar by the symbol Expr.
[39] | Expr |
::= | ExprSingle (","
ExprSingle)* |
[40] | ExprSingle |
::= | FLWORExpr |
The XQuery 3.0 operator that has lowest precedence is the comma operator, which is used to combine two operands to form a sequence. As shown in the grammar, a general expression (Expr) can consist of multiple ExprSingle operands, separated by commas. The name ExprSingle denotes an expression that does not contain a top-level comma operator (despite its name, an ExprSingle may evaluate to a sequence containing more than one item.)
The symbol ExprSingle is used in various places in the grammar where an expression is not allowed to contain a top-level comma. For example, each of the arguments of a function call must be an ExprSingle, because commas are used to separate the arguments of a function call.
After the comma, the expressions that have next lowest precedence are FLWORExpr, QuantifiedExpr, SwitchExpr, TypeswitchExpr, IfExpr, TryCatchExpr, and OrExpr. Each of these expressions is described in a separate section of this document.
[Definition: Primary expressions are the basic primitives of the language. They include literals, variable references, context item expressions, constructors, and function calls. A primary expression may also be created by enclosing any expression in parentheses, which is sometimes helpful in controlling the precedence of operators.] Constructors are described in 3.8 Constructors.
[121] | PrimaryExpr |
::= | Literal |
[160] | FunctionItemExpr |
::= | LiteralFunctionItem |
InlineFunction |
[Definition: A literal is a direct syntactic representation of an atomic value.] XQuery 3.0 supports two kinds of literals: numeric literals and string literals.
[122] | Literal |
::= | NumericLiteral
| StringLiteral |
[123] | NumericLiteral |
::= | IntegerLiteral
| DecimalLiteral |
DoubleLiteral |
[194] | IntegerLiteral |
::= | Digits |
[195] | DecimalLiteral |
::= | ("." Digits) |
(Digits "." [0-9]*) |
[196] | DoubleLiteral |
::= | (("." Digits) |
(Digits ("." [0-9]*)?)) [eE]
[+-]? Digits |
[197] | StringLiteral |
::= | ('"' (PredefinedEntityRef |
CharRef | EscapeQuot | [^"&])* '"') | ("'"
(PredefinedEntityRef |
CharRef | EscapeApos | [^'&])*
"'") |
[198] | PredefinedEntityRef |
::= | "&" ("lt" | "gt" | "amp" | "quot" | "apos")
";" |
[199] | EscapeQuot |
::= | '""' |
[200] | EscapeApos |
::= | "''" |
[211] | Digits |
::= | [0-9]+ |
The value of a numeric literal containing no
".
" and no e
or E
character
is an atomic value of type xs:integer
. The value of a
numeric literal containing ".
" but no e
or E
character is an atomic value of type
xs:decimal
. The value of a numeric literal containing
an e
or E
character is an atomic value of
type xs:double
. The value of the numeric literal is
determined by casting it to the appropriate type according to the
rules for casting from xs:untypedAtomic
to a numeric
type as specified in Section
18.1.1 Casting from xs:string and xs:untypedAtomic
FO30.
The value of a string literal is
an atomic value whose type is xs:string
and whose
value is the string denoted by the characters between the
delimiting apostrophes or quotation marks. If the literal is
delimited by apostrophes, two adjacent apostrophes within the
literal are interpreted as a single apostrophe. Similarly, if the
literal is delimited by quotation marks, two adjacent quotation
marks within the literal are interpreted as one quotation mark.
A string literal may contain a predefined entity reference. [Definition: A predefined entity reference is a short sequence of characters, beginning with an ampersand, that represents a single character that might otherwise have syntactic significance.] Each predefined entity reference is replaced by the character it represents when the string literal is processed. The predefined entity references recognized by XQuery are as follows:
Entity Reference | Character Represented |
< |
< |
> |
> |
& |
& |
" |
" |
' |
' |
A string literal may also contain a character
reference. [Definition: A character reference
is an XML-style reference to a [Unicode]
character, identified by its decimal or hexadecimal codepoint.] For
example, the Euro symbol (€) can be represented by the character
reference €
. Character references are
normatively defined in Section 4.1 of the XML specification (it is
implementation-defined whether the
rules in [XML 1.0] or [XML
1.1] apply.) A static error [err:XQST0090] is raised if a character reference
does not identify a valid character in the version of XML that is
in use.
Here are some examples of literal expressions:
"12.5"
denotes the string containing the characters
'1', '2', '.', and '5'.
12
denotes the xs:integer
value
twelve.
12.5
denotes the xs:decimal
value
twelve and one half.
125E2
denotes the xs:double
value
twelve thousand, five hundred.
"He said, ""I don't like it."""
denotes a string
containing two quotation marks and one apostrophe.
"Ben & Jerry's"
denotes the
xs:string
value "Ben & Jerry's
".
"€99.50"
denotes the
xs:string
value "€99.50
".
The xs:boolean
values true
and
false
can be constructed by calls to the built-in
functions fn:true()
and fn:false()
,
respectively.
Values of other atomic types can be constructed by calling the constructor function for the given type. The constructor functions for XML Schema built-in types are defined in [XQuery and XPath Functions and Operators 3.0]. In general, the name of a constructor function for a given type is the same as the name of the type (including its namespace). For example:
xs:integer("12")
returns the integer value
twelve.
xs:date("2001-08-25")
returns an item whose type is
xs:date
and whose value represents the date 25th
August 2001.
xs:dayTimeDuration("PT5H")
returns an item whose
type is xs:dayTimeDuration
and whose value represents
a duration of five hours.
Constructor functions can also be used to create special values that have no literal representation, as in the following examples:
xs:float("NaN")
returns the special floating-point
value, "Not a Number."
xs:double("INF")
returns the special
double-precision value, "positive infinity."
It is also possible to construct values of various types by
using a cast
expression. For example:
9 cast as hatsize
returns the atomic value
9
whose type is hatsize
.
[124] | VarRef |
::= | "$" VarName |
[125] | VarName |
::= | EQName |
[Definition: A variable reference is an EQName preceded by a $-sign.] Two variable references are equivalent if their local names are the same and their namespace prefixes are bound to the same namespace URI in the statically known namespaces. An unprefixed variable reference is in no namespace.
Every variable reference must match a name in the in-scope variables, which include variables from the following sources:
A variable may be declared in a Prolog, in the current module or an imported module. See 4 Modules and Prologs for a discussion of modules and Prologs.
The in-scope variables may be augmented by implementation-defined variables.
A variable may be bound by an XQuery 3.0 expression.
The kinds of expressions that can bind
variables are FLWOR expressions (3.9 FLWOR Expressions),
quantified expressions (3.13 Quantified
Expressions), and typeswitch
expressions
(3.15.2 Typeswitch). Function
calls also bind values to the formal parameters of functions before
executing the function body.
Every variable binding has a static scope. The scope defines where references to the variable can validly occur. It is a static error [err:XPST0008] to reference a variable that is not in scope. If a variable is bound in the static context for an expression, that variable is in scope for the entire expression.
A reference to a variable that was declared
external
, but was not bound to a value by the external
environment, raises a dynamic error [err:XPDY0002].
If a variable reference matches two or more variable bindings that are in scope, then the reference is taken as referring to the inner binding, that is, the one whose scope is smaller. At evaluation time, the value of a variable reference is the value of the expression to which the relevant variable is bound. The scope of a variable binding is defined separately for each kind of expression that can bind variables.
[126] | ParenthesizedExpr |
::= | "(" Expr?
")" |
Parentheses may be used to override the precedence rules. For
example, the expression (2 + 4) * 5
evaluates to
thirty, since the parenthesized expression (2 + 4)
is
evaluated first and its result is multiplied by five. Without
parentheses, the expression 2 + 4 * 5
evaluates to
twenty-two, because the multiplication operator has higher
precedence than the addition operator.
Empty parentheses are used to denote an empty sequence, as described in 3.4.1 Constructing Sequences.
[127] | ContextItemExpr |
::= | "." |
A context item expression evaluates to the context item, which may
be either a node (as in the expression
fn:doc("bib.xml")/books/book[fn:count(./author)>1]
),
or an atomic value or function item (as in the expression (1
to 100)[. mod 5 eq 0]
).
If the context item is undefined, a context item expression raises a dynamic error [err:XPDY0002].
[Definition: The built-in functions supported by XQuery 3.0 are defined in [XQuery and XPath Functions and Operators 3.0].] Additional functions may be declared in a Prolog, imported from a library module, or provided by the external environment as part of the static context.
[130] | FunctionCall |
::= | EQName ArgumentList |
[131] | Argument |
::= | ExprSingle |
ArgumentPlaceholder |
[132] | ArgumentPlaceholder |
::= | "?" |
A function call consists of an EQName followed by a parenthesized list of zero or more arguments. [Definition: An argument to a function call is either an argument expression or an ArgumentPlaceholder ("?").] If the EQName in the function call has no namespace prefix, it is considered to be in the default function namespace.
If the expanded QName and number of arguments in a function call do not match the name and arity of a function signature in the static context, a static error is raised [err:XPST0017].
[Definition: A function call is a partial function application if one or more arguments is an ArgumentPlaceholder.] Evaluation of partial function applications is described in 3.1.5.4 Evaluating Partial Function Applications, while evaluation of (non-partial) function calls is described in 3.1.5.1 Evaluating Function Calls.
Since the arguments of a function call are separated by commas, any argument expression that contains a top-level comma operator must be enclosed in parentheses. Here are some illustrative examples of function calls:
my:three-argument-function(1, 2, 3)
denotes a
function call with three arguments.
my:two-argument-function((1, 2), 3)
denotes a
function call with two arguments, the first of which is a sequence
of two values.
my:two-argument-function(1, ())
denotes a function
call with two arguments, the second of which is an empty
sequence.
my:one-argument-function((1, 2, 3))
denotes a
function call with one argument that is a sequence of three
values.
my:one-argument-function(( ))
denotes a function
call with one argument that is an empty sequence.
my:zero-argument-function( )
denotes a function
call with zero arguments.
The result of a function call on a function or function
itemDM30 $f
is
calculated as follows:
[Definition: Argument expressions are evaluated, producing argument values.] The order of argument evaluation is implementation-dependent and a function need not evaluate an argument if the function can evaluate its body without evaluating that argument.
Each argument value is converted by applying the function conversion rules.
If $f
is a function
itemDM30, then the set of variable
values from the function item's closureDM30
are added to the dynamic context with a scope of the invocation of
the function.
If $f
is a built-in function, it is evaluated using
the converted argument values. The result is either an instance of
the function's declared return type or a dynamic error. Errors
raised by built-in functions are defined in [XQuery and XPath Functions and Operators
3.0].
If $f
is an inline function or
user-defined
function , the converted argument values are bound to
the formal parameters of $f
, and the function body is
evaluated. The value returned by the function body is then
converted to the declared return type of $f
by
applying the function conversion rules.
When a converted argument value is bound to a function
parameter, the argument value retains its most specific dynamic type, even
though this type may be derived from the type of the formal
parameter. For example, a function with a parameter $p
of type xs:decimal
can be invoked with an argument of
type xs:integer
, which is derived from
xs:decimal
. During the processing of this function
invocation, the dynamic type of $p
inside the
body of the function is considered to be xs:integer
.
Similarly, the value returned by a function retains its most
specific type, which may be derived from the declared return type
of $f
. For example, a function that has a declared
return type of xs:decimal
may in fact return a value
of dynamic type xs:integer
.
During evaluation of a function body, the static context and dynamic context for expression evaluation are defined by the module or expression in which the function is declared, which is not necessarily the same as the context in which the function is called. For example, the variables in scope while evaluating a function body are defined by the in-scope variables where it is declared, rather than those in scope where the function is called. During evaluation of a function body, the focus (context item, context position, and context size) is undefined, except where it is defined by some expression inside the function body.
If $f
is an external function, its function implementation is
invoked with the converted argument values. The result is either a
value of the declared type or an implementation-defined error
(see 2.2.5 Consistency
Constraints).
[Definition: The function conversion rules are used to convert an argument value or a return value to its expected type; that is, to the declared type of the function parameter or return. ] The expected type is expressed as a sequence type. The function conversion rules are applied to a given value as follows:
If the expected type is a sequence of an atomic type (possibly
with an occurrence indicator *
, +
, or
?
), the following conversions are applied:
Atomization is applied to the given value, resulting in a sequence of atomic values.
Each item in the atomic sequence that is of type
xs:untypedAtomic
is cast to the expected atomic type.
For built-in functions where the expected
type is specified as numeric, arguments of type
xs:untypedAtomic
are cast to xs:double
.
If the item is of type xs:untypedAtomic
and the
expected type is namespace-sensitive, a type error [err:XPTY0117] is
raised.
For each numeric item in the atomic sequence that can be promoted to the expected atomic type using numeric promotion as described in B.1 Type Promotion, the promotion is done.
For each item of type xs:anyURI
in the atomic
sequence that can be promoted to the expected atomic type using
URI promotion as described in B.1 Type
Promotion, the promotion is done.
If the expected type is a TypedFunctionTest (possibly
with an occurrence indicator *
, +
, or
?
), function item coercion is applied
to each function item in the given value.
If, after the above conversions, the resulting value does not match the expected type according to the rules for SequenceType Matching, a type error is raised [err:XPTY0004]. If the function call takes place in a module other than the module in which the function is defined, this rule must be satisfied in both the module where the function is called and the module where the function is defined (the test is repeated because the two modules may have different in-scope schema definitions.) Note that the rules for SequenceType Matching permit a value of a derived type to be substituted for a value of its base type.
Function item coercion is a transformation applied to function itemsDM30 during application of the function conversion rules. [Definition: Function item coercion wraps a function itemDM30 in a new inline function with signature the same as the expected type. This effectively delays the checking of the argument and return types until the function item is invoked.]
Function item coercion is only defined to operate on function
itemsDM30. Given a function item,
$function
, function item coercion returns a new
function item with the following properties (as defined in Section
2.8.1 Function Items DM30):
An empty set of variable values.
The name of $function
.
A function signatureDM30 equal to the expected type for the function argument or return type.
A function implementation whose result is calculated by invoking
$function
with the arguments that were specified at
the new function's invocation.
If the result of invoking the new function item would necessarily result in a type error, that error may be raised during function coercion. It is implementation dependent whether this happens or not.
These rules have the following consequences:
SequenceType matching of the function item's arguments and result are delayed until that function item is invoked.
The function conversion rules applied to the function item's arguments and result are defined by the SequenceType it has most recently been coerced to. Additional function conversion rules could apply when the wrapped function item is invoked.
If an implementation has static type information about a function item, that can be used to type check the function item's argument and return types during static analysis.
For instance, consider the following query:
declare function local:filter($s as item()*, $p as function(xs:string) as xs:boolean) as item()* { $s[$p(.)] }; let $f := function($a) { starts-with($a, "E") } return local:filter(("Ethel", "Enid", "Gertrude"), $f)
The function item $f
has a static type of
function(item()*) as item()*
. When the
local:filter()
function is called, the following
occurs to the function item:
The function conversion rules result in applying function
coercion to $function
, wrapping $f in a new inline
function ($p) with the signature function(xs:string) as
xs:boolean
.
$p is matched against the SequenceType of
function(xs:string) as xs:boolean
, and succeeds.
When $p is invoked inside the predicate, function conversion and
SequenceType matching rules are applied to the context item
argument, resulting in an xs:string
value or a type
error.
$f is invoked with the xs:string
, which returns an
xs:boolean
.
$p applies function conversion rules to the result sequence from
$f, which already matches its declared return type of
xs:boolean
.
The xs:boolean
is returned as the result of $p.
Note:
Although the semantics of function item coercion are specified in terms of wrapping the function items, static typing will often be able to reduce the number of places where this is actually necessary.
The result of a partial function application
of a function or function
itemDM30 $f
is computed
as follows:
The argument expressions supplied are evaluated, producing argument values.
A single function item $new
is returned, with the
following properties (as defined in Section
2.8.1 Function Items DM30):
An empty set of variable values.
An absent name.
The function
signatureDM30 of $new
is
the same as $f
, removing the parameters in the
positions for which any argument expressions have been provided to the
partial function application. The function arity of
$new
is the arity of $f
minus the number
of argument expressions provided.
A function implementation which invokes $f
with the
argument expressions from the invocation of $new
,
inserting any argument values from the partial function
application in their respective positions.
If the value of any argument expression specified to a partial
function application cannot be converted to the required type of
the corresponding argument of $f
by applying the
function conversion rules, then a
type error [err:XPTY0004] MAY be raised. (If a type error is not
raised at this stage, it will be raised later when the new function
is invoked.)
The static context for evaluation of the function item
$f
is inherited from the location of the partial
function application expression, with the exception of the static
type of the context item which is initially undefined.
Partially applied function items cannot access the focus (context item, context position, and context size), which is undefined when they are invokedDM30. It is a static error to partially apply a function which accesses the focus [err:XPST0112].
[161] | LiteralFunctionItem |
::= | EQName "#" IntegerLiteral |
[192] | EQName |
::= | QName | URIQualifiedName |
[Definition: A literal function item creates a function itemDM30 that represents a named function.] [Definition: A named function is a function defined in the static context for the query. To uniquely identify a particular named function, both its name as a QName and its arity are required.]
If the EQName is a lexical QName that has no namespace prefix, it is considered to be in the default function namespace.
If the expanded QName and arity in a literal function item do not match the name and arity of a function signature in the static context, a static error is raised [err:XPST0017].
The result of a literal function item is a single function item with the following properties (as defined in Section 2.8.1 Function Items DM30):
An empty set of variable values.
The name specified in the literal function item.
The function signatureDM30 of the function from the static context that matches the name and arity given.
The implementation of the function from the static context that matches the name and arity given.
The static context for evaluation of the function item is inherited from the location of the literal function item expression, with the exception of the static type of the context item which is initially undefined.
Literal function items cannot access the focus (context item, context position, and context size), which is undefined when they are invokedDM30. It is a static error to create a function item for a function which accesses the focus [err:XPST0112].
Note:
User-defined functions cannot access the focus, so this error only applies to built-in functions like:
fn:position#0
fn:last#0
fn:name#0
fn:namespace-uri#0
fn:local-name#0
fn:number#0
fn:string#0
fn:string-length#0
fn:normalize-space#0
fn:root#0
fn:id#1
fn:idref#1
fn:lang#1
fn:base-uri#0
Certain functions in the [XQuery and XPath Functions and Operators 3.0] specification are defined to be polymorphic. These are denoted as accepting parameters of "numeric" type, or returning "numeric" type. Here "numeric" is a pseudonym for the four primitive numeric types xs:decimal, xs:integer, xs:float, and xs:double. The functions in question are:
fn:abs
fn:ceiling
fn:floor
fn:round
fn:round-half-to-even
For the purposes of literal function items, these functions are regarded as taking arguments and producing results of type xs:anyAtomicType, with a type error raised at runtime if the argument value provided is not of the correct numeric type.
Note:
The above way of modeling polymorphic functions is semantically backwards compatible with XQuery 1.0. An implementation that supports static typing can choose to model the types of these functions more accurately if desired.
The following are examples of some literal function item expressions:
fn:abs#1
references the fn:abs function which takes
a single argument.
fn:concat#5
references the fn:concat function which
takes 5 arguments.
local:myfunc#2
references a function named
local:myfunc which takes 2 arguments.
[162] | InlineFunction |
::= | "function" "(" ParamList? ")" ("as" SequenceType)? EnclosedExpr |
[Definition: An inline function expression creates a function itemDM30 that represents an anonymous function defined directly in the inline function expression itself.] An inline function specifies the names and SequenceTypes of the parameters to the function, the SequenceType of the result, and the body of the function.
If a function parameter is declared using a name but no type, its default type is item()*. If the result type is omitted from a function declaration, its default result type is item()*.
The parameters of a function declaration are considered to be variables whose scope is the function body. It is a static error [err:XQST0039] for a function declaration to have more than one parameter with the same name.
The static context for the function body is inherited from the location of the inline function expression, with the exception of the static type of the context item which is initially undefined.
The variables in scope for the function body include all variables representing the function parameters, as well as all variables that are in scope for the inline function expression.
Note:
Function parameter names can mask variables that would otherwise be in scope for the function body.
The result of an inline function is a single function item with the following properties (as defined in Section 2.8.1 Function Items DM30):
The set of variable values for any variables referenced by the inline function's body.
An absent name.
The function signatureDM30 of the inline function.
An implementation derived from the body of the inline function.
The following are examples of some inline functions:
This example creates an inline function that takes no arguments and returns a sequence of the first 6 primes:
function() as xs:integer+ { 2, 3, 5, 7, 11, 13 }
This example creates an inline function that takes two xs:double arguments and returns their product:
function($a as xs:double, $b as xs:double) as xs:double { $a * $b }
This example creates an inline function that returns its item()* argument:
function($a) { $a }
This example creates an inline function that returns the xs:integer value 7, i.e.: the value of the variable $a from the scope of the inline function expression:
let $a := 7 return let $f := function() { $a } return let $a := 8 return $f()
[117] | PostfixExpr |
::= | PrimaryExpr
(Predicate | ArgumentList)* |
[120] | Predicate |
::= | "[" Expr "]" |
[118] | ArgumentList |
::= | "(" (Argument (","
Argument)*)? ")" |
[Definition: An expression followed by a
predicate (that is, E1[E2]
) is referred to as a
filter expression: its effect is to return those items from
the value of E1
that satisfy the predicate in E2.]
Filter expressions are described in 3.2.1 Filter Expressions
[Definition: An expression (other
than a raw EQName) followed by an argument list in parentheses
(that is, E1(E2, E3, ...)
) is referred to as a
dynamic function invocation. Its effect is to evaluate
E1
to obtain a function item, and then call the
function represented by that function item, with E2
,
E3
, ...
as arguments.] Dynamic function
invocations are described in 3.2.2 Dynamic Function
Invocation.
[117] | PostfixExpr |
::= | PrimaryExpr
(Predicate | ArgumentList)* |
[120] | Predicate |
::= | "[" Expr "]" |
A filter expression consists of a base expression followed by a predicate, which is an expression written in square brackets. The result of the filter expression consists of the items returned by the base expression, filtered by applying the predicate to each item in turn. The ordering of the items returned by a filter expression is the same as their order in the result of the primary expression.
Note:
Where the expression before the square brackets is a ReverseStep or ForwardStep, the expression is technically not a filter expression but an AxisStep. There are minor differences in the semantics: see 3.3.2 Predicates within Steps
Here are some examples of filter expressions:
Given a sequence of products in a variable, return only those products whose price is greater than 100.
$products[price gt 100]
List all the integers from 1 to 100 that are divisible by 5.
(See 3.4.1 Constructing
Sequences for an explanation of the to
operator.)
(1 to 100)[. mod 5 eq 0]
The result of the following expression is the integer 25:
(21 to 29)[5]
The following example returns the fifth through ninth items in
the sequence bound to variable $orders
.
$orders[fn:position() = (5 to 9)]
The following example illustrates the use of a filter expression
as a step in a path expression.
It returns the last chapter or appendix within the book bound to
variable $book
:
$book/(chapter | appendix)[fn:last()]
The following example also illustrates the use of a filter
expression as a step in a
path
expression. It returns the element node within the specified
document whose ID value is tiger
:
fn:doc("zoo.xml")/fn:id('tiger')
For each item in the input sequence, the predicate expression is evaluated using an inner focus, defined as follows: The context item is the item currently being tested against the predicate. The context size is the number of items in the input sequence. The context position is the position of the context item within the input sequence.
For each item in the input sequence, the result of the predicate
expression is coerced to an xs:boolean
value, called
the predicate truth value, as described below. Those items
for which the predicate truth value is true
are
retained, and those for which the predicate truth value is
false
are discarded.
The predicate truth value is derived by applying the following rules, in order:
If the value of the predicate expression is a singleton atomic value of a
numeric type or derived
from a numeric type, the
predicate truth value is true
if the value of the
predicate expression is equal (by the eq
operator) to
the context position, and is false
otherwise.
[Definition: A predicate whose predicate
expression returns a numeric type is called a numeric
predicate.]
Note:
In a region of a query where ordering mode is unordered
,
the result of a numeric predicate is nondeterministic, as explained
in 3.10 Ordered and
Unordered Expressions.
Otherwise, the predicate truth value is the effective boolean value of the predicate expression.
[117] | PostfixExpr |
::= | PrimaryExpr
(Predicate | ArgumentList)* |
[118] | ArgumentList |
::= | "(" (Argument (","
Argument)*)? ")" |
[131] | Argument |
::= | ExprSingle |
ArgumentPlaceholder |
[132] | ArgumentPlaceholder |
::= | "?" |
[Definition: A dynamic function invocation consists of a PrimaryExpr that returns the function item and a parenthesized list of zero or more arguments (argument expressions or ArgumentPlaceholders).]
If the PrimaryExpr does not return a sequence consisting of a single function item with the same arity as the number of specified arguments, a type error is raised [err:XPTY0004].
A dynamic function invocation is a partial function application if at least one of the arguments is an ArgumentPlaceholder ("?"), and is evaluated according to the rules in 3.1.5.4 Evaluating Partial Function Applications.
A dynamic function invocation that is not a partial function application invokesDM30 the function itemDM30, calling the function it represents, and is evaluated as described in 3.1.5.1 Evaluating Function Calls.
The following are examples of some dynamic function invocations:
This example invokes the function item contained in $f, passing the arguments 2 and 3:
$f(2, 3)
This example fetches the second item from sequence $f, treats it
as a function item and invokes it, passing an
xs:string
argument:
$f[2]("Hi there")
This example invokes the function item $f passing no arguments, and filters the result with a positional predicate:
$f()[2]
[104] | PathExpr |
::= | ("/" RelativePathExpr?) |
[105] | RelativePathExpr |
::= | StepExpr (("/" |
"//") StepExpr)* |
[Definition: A path expression can be
used to locate nodes within trees. A path expression consists of a
series of one or more steps,
separated by "/
" or "//
", and optionally
beginning with "/
" or "//
".] An initial
"/
" or "//
" is an abbreviation for one or
more initial steps that are implicitly added to the beginning of
the path expression, as described below.
A path expression consisting of a single step is evaluated as described in 3.3.1 Steps.
A "/
" at the beginning of a path expression is an
abbreviation for the initial step
(fn:root(self::node()) treat as
document-node())/
(however, if the "/
"
is the entire path expression, the trailing "/
" is
omitted from the expansion.) The effect of this initial step is to
begin the path at the root node of the tree that contains the
context node. If the context item is not a node, a type error is raised
[err:XPTY0020]. At
evaluation time, if the root node above the context node is not a
document node, a dynamic error is raised [err:XPDY0050].
A "//
" at the beginning of a path expression is an
abbreviation for the initial steps
(fn:root(self::node()) treat as
document-node())/descendant-or-self::node()/
(however, "//
" by itself is not a valid path
expression [err:XPST0003].) The effect of these initial
steps is to establish an initial node sequence that contains the
root of the tree in which the context node is found, plus all nodes
descended from this root. This node sequence is used as the input
to subsequent steps in the path expression. If the context item is
not a node, a type
error is raised [err:XPTY0020]. At evaluation time, if the root
node above the context node is not a document node, a dynamic error is
raised [err:XPDY0050].
Note:
The descendants of a node do not include attribute nodes .
Each non-initial occurrence of "//
" in a path
expression is expanded as described in 3.3.4
Abbreviated Syntax, leaving a sequence of steps separated
by "/
". This sequence of steps is then evaluated from
left to right. Each operation E1/E2
is evaluated as
follows: Expression E1
is evaluated, and if the result
is not a (possibly empty) sequence of nodes, a type error is raised
[err:XPTY0019].
Each node resulting from the evaluation of E1
then
serves in turn to provide an inner focus for an evaluation
of E2
, as described in 2.1.2 Dynamic Context. The sequences
resulting from all the evaluations of E2
are combined
as follows:
If every evaluation of E2
returns a (possibly
empty) sequence of nodes, these sequences are combined, and
duplicate nodes are eliminated based on node identity. If ordering mode is ordered
, the
resulting node sequence is returned in document order; otherwise it is
returned in implementation-dependent
order.
If every evaluation of E2
returns a (possibly
empty) sequence of non-nodes, these sequences are concatenated and
returned. If ordering mode is ordered
, the
returned sequence preserves the orderings within and among the
subsequences generated by the evaluations of E2
;
otherwise the order of the returned sequence is implementation-dependent.
If the multiple evaluations of E2
return at least
one node and at least one non-node, a type error is raised [err:XPTY0018].
Note:
Since each step in a path provides context nodes for the following step, in effect, only the last step in a path is allowed to return a sequence of non-nodes.
As an example of a path expression,
child::div1/child::para
selects the para
element children of the div1
element children of the
context node, or, in other words, the para
element
grandchildren of the context node that have div1
parents.
Note:
The "/
" character can be used
either as a complete path expression or as the beginning of a
longer path expression such as "/*
". Also,
"*
" is both the multiply operator and a wildcard in
path expressions. This can cause parsing difficulties when
"/
" appears on the left hand side of "*
".
This is resolved using the leading-lone-slash constraint.
For example, "/*
" and "/ *
" are valid
path expressions containing wildcards, but "/*5
" and
"/ * 5
" raise syntax errors. Parentheses must be used
when "/
" is used on the left hand side of an operator,
as in "(/) * 5
". Similarly, "4 + / * 5
"
raises a syntax error, but "4 + (/) * 5
" is a valid
expression. The expression "4 + /
" is also valid,
because /
does not occur on the left hand side of the
operator.
Similarly, in the expression / union /*
, "union" is
interpreted as an element name rather than an operator. For it to
be parsed as an operator, the expression should be written
(/) union /*
.
[106] | StepExpr |
::= | PostfixExpr |
AxisStep |
[107] | AxisStep |
::= | (ReverseStep |
ForwardStep) PredicateList |
[108] | ForwardStep |
::= | (ForwardAxis
NodeTest) | AbbrevForwardStep |
[111] | ReverseStep |
::= | (ReverseAxis
NodeTest) | AbbrevReverseStep |
[119] | PredicateList |
::= | Predicate* |
[Definition: A step is a part of a path expression that generates a sequence of items and then filters the sequence by zero or more predicates. The value of the step consists of those items that satisfy the predicates, working from left to right. A step may be either an axis step or a postfix expression.] Postfix expressions are described in 3.2 Postfix Expressions.
[Definition: An axis step returns a sequence
of nodes that are reachable from the context node via a specified
axis. Such a step has two parts: an axis, which defines the
"direction of movement" for the step, and a node test, which selects nodes based on
their kind, name, and/or type annotation.] If the context item is
a node, an axis step returns a sequence of zero or more nodes;
otherwise, a type
error is raised [err:XPTY0020]. If ordering mode is
ordered
, the resulting node sequence is returned in
document
order; otherwise it is returned in implementation-dependent
order. An axis step may be either a forward step or a
reverse step, followed by zero or more predicates.
In the abbreviated syntax for a step, the axis can be omitted and other shorthand notations can be used as described in 3.3.4 Abbreviated Syntax.
The unabbreviated syntax for an axis step consists of the axis
name and node test separated by a double colon. The result of the
step consists of the nodes reachable from the context node via the
specified axis that have the node kind, name, and/or type annotation
specified by the node test. For example, the step
child::para
selects the para
element
children of the context node: child
is the name of the
axis, and para
is the name of the element nodes to be
selected on this axis. The available axes are described in 3.3.1.1 Axes. The available node tests are
described in 3.3.1.2 Node Tests.
Examples of steps are provided in 3.3.3
Unabbreviated Syntax and 3.3.4
Abbreviated Syntax.
[109] | ForwardAxis |
::= | ("child" "::") |
[112] | ReverseAxis |
::= | ("parent" "::") |
XQuery supports the following axes:
The child
axis contains the children of the context
node, which are the nodes returned by the dm:children
accessor in [XQuery and XPath Data
Model (XDM) 3.0].
Note:
Only document nodes and element nodes have children. If the context node is any other kind of node, or if the context node is an empty document or element node, then the child axis is an empty sequence. The children of a document node or element node may be element, processing instruction, comment, or text nodes. Attribute and document nodes can never appear as children.
the descendant
axis is defined as the transitive
closure of the child axis; it contains the descendants of the
context node (the children, the children of the children, and so
on)
the parent
axis contains the sequence returned by
the dm:parent
accessor in [XQuery and XPath Data Model (XDM) 3.0],
which returns the parent of the context node, or an empty sequence
if the context node has no parent
Note:
An attribute node may have an element node as its parent, even though the attribute node is not a child of the element node.
the ancestor
axis is defined as the transitive
closure of the parent axis; it contains the ancestors of the
context node (the parent, the parent of the parent, and so on)
Note:
The ancestor axis includes the root node of the tree in which the context node is found, unless the context node is the root node.
the following-sibling
axis contains the context
node's following siblings, those children of the context node's
parent that occur after the context node in document order; if
the context node is an attribute node, the
following-sibling
axis is empty
the preceding-sibling
axis contains the context
node's preceding siblings, those children of the context node's
parent that occur before the context node in document order; if
the context node is an attribute node, the
preceding-sibling
axis is empty
the following
axis contains all nodes that are
descendants of the root of the tree in which the context node is
found, are not descendants of the context node, and occur after the
context node in document order
the preceding
axis contains all nodes that are
descendants of the root of the tree in which the context node is
found, are not ancestors of the context node, and occur before the
context node in document order
the attribute
axis contains the attributes of the
context node, which are the nodes returned by the
dm:attributes
accessor in [XQuery and XPath Data Model (XDM) 3.0];
the axis will be empty unless the context node is an element
the self
axis contains just the context node
itself
the descendant-or-self
axis contains the context
node and the descendants of the context node
the ancestor-or-self
axis contains the context node
and the ancestors of the context node; thus, the ancestor-or-self
axis will always include the root node
Axes can be categorized as forward axes and reverse axes. An axis that only ever contains the context node or nodes that are after the context node in document order is a forward axis. An axis that only ever contains the context node or nodes that are before the context node in document order is a reverse axis.
The parent
, ancestor
,
ancestor-or-self
, preceding
, and
preceding-sibling
axes are reverse axes; all other
axes are forward axes. The ancestor
,
descendant
, following
,
preceding
and self
axes partition a
document (ignoring attribute nodes): they do not overlap and
together they contain all the nodes in the document.
[Definition: Every axis has a principal node kind. If an axis can contain elements, then the principal node kind is element; otherwise, it is the kind of nodes that the axis can contain.] Thus:
For the attribute axis, the principal node kind is attribute.
For all other axes, the principal node kind is element.
[Definition: A node test is a condition that must be true for each node selected by a step.] The condition may be based on the kind of the node (element, attribute, text, document, comment, or processing instruction), the name of the node, or (in the case of element, attribute, and document nodes), the type annotation of the node.
[114] | NodeTest |
::= | KindTest | NameTest |
[115] | NameTest |
::= | EQName | Wildcard |
[116] | Wildcard |
::= | "*" |
[192] | EQName |
::= | QName | URIQualifiedName |
[Definition: A node test that consists only of a
EQName or a Wildcard is called a name test.] A name test is
true if and only if the kind of the node is the principal node
kind for the step axis and the expanded QName of the node is equal (as
defined by the eq
operator) to the expanded QName
specified by the name test. For example, child::para
selects the para
element children of the context node;
if the context node has no para
children, it selects
an empty set of nodes. attribute::abc:href
selects the
attribute of the context node with the QName abc:href
;
if the context node has no such attribute, it selects an empty set
of nodes.
If the EQName is a lexical QName, it is resolved into an expanded QName using
the statically known namespaces in the
expression context. It is a static error [err:XPST0081] if the QName has a prefix that
does not correspond to any statically known namespace. It is a
static error
[err:XQST0070] if
the URILiteral for an EQName is
http://www.w3.org/2000/xmlns/
. An unprefixed QName,
when used as a name test on an axis whose principal node
kind is element, has the namespace URI of the default
element/type namespace in the expression context; otherwise, it
has no namespace URI.
A name test is not satisfied by an element node whose name does not match the expanded QName of the name test, even if it is in a substitution group whose head is the named element.
A node test *
is true for any node of the principal node
kind of the step axis. For example, child::*
will
select all element children of the context node, and
attribute::*
will select all attributes of the context
node.
A node test can have the form NCName:*
. In this
case, the prefix is expanded in the same way as with a lexical QName, using the
statically known namespaces in the
static
context. If the prefix is not found in the statically known
namespaces, a static error is raised [err:XPST0081]. The node
test is true for any node of the principal node kind of the step
axis whose expanded QName has the namespace URI to
which the prefix is bound, regardless of the local part of the
name.
A node test can contain a URILiteral, e.g.
"http://example.com/msg":*
Such a node test is true
for any node of the principal node kind of the step axis whose
expanded QName has the namespace URI specified in the URILiteral,
regardless of the local part of the name.
A node test can also have the form *:NCName
. In
this case, the node test is true for any node of the principal node
kind of the step axis whose local name matches the given
NCName, regardless of its namespace or lack of a namespace.
[Definition: An alternative form of a node test called a kind test can select nodes based on their kind, name, and type annotation.] The syntax and semantics of a kind test are described in 2.5.4 SequenceType Syntax and 2.5.5 SequenceType Matching. When a kind test is used in a node test, only those nodes on the designated axis that match the kind test are selected. Shown below are several examples of kind tests that might be used in path expressions:
node()
matches any node.
text()
matches any text node.
comment()
matches any comment node.
namespace-node()
matches any namespace node.
element()
matches any element node.
schema-element(person)
matches any element node
whose name is person
(or is in the substitution
group headed by person
), and whose type annotation
is the same as (or is derived from) the declared type of the
person
element in the in-scope
element declarations.
element(person)
matches any element node whose name
is person
, regardless of its type annotation.
element(person, surgeon)
matches any non-nilled
element node whose name is person
, and whose type
annotation is surgeon
or is derived from
surgeon
.
element(*, surgeon)
matches any non-nilled element
node whose type annotation is surgeon
(or is derived
from surgeon
), regardless of its name.
attribute()
matches any attribute node.
attribute(price)
matches any attribute whose name
is price
, regardless of its type annotation.
attribute(*, xs:decimal)
matches any attribute
whose type annotation is xs:decimal
(or is derived
from xs:decimal
), regardless of its name.
document-node()
matches any document node.
document-node(element(book))
matches any document
node whose content consists of a single element node that satisfies
the kind test
element(book)
, interleaved with zero or more comments
and processing instructions.
[107] | AxisStep |
::= | (ReverseStep |
ForwardStep) PredicateList |
[119] | PredicateList |
::= | Predicate* |
[120] | Predicate |
::= | "[" Expr "]" |
A predicate within a Step has similar syntax and semantics to a predicate within a filter expression. The only difference is in the way the context position is set for evaluation of the predicate.
For the purpose of evaluating the context position within a predicate, the input sequence is considered to be sorted as follows: into document order if the predicate is in a forward-axis step, into reverse document order if the predicate is in a reverse-axis step, or in its original order if the predicate is not in a step.
Here are some examples of axis steps that contain predicates:
This example selects the second chapter
element
that is a child of the context node:
child::chapter[2]
This example selects all the descendants of the context node
that are elements named "toy"
and whose
color
attribute has the value "red"
:
descendant::toy[attribute::color = "red"]
This example selects all the employee
children of
the context node that have both a secretary
child
element and an assistant
child element:
child::employee[secretary][assistant]
Note:
When using predicates with
a sequence of nodes selected using a reverse axis, it is
important to remember that the the context positions for such a
sequence are assigned in reverse document order. For
example, preceding::foo[1]
returns the first
qualifying foo
element in reverse
document order, because the predicate is part of an axis step using a reverse
axis. By contrast, (preceding::foo)[1]
returns the
first qualifying foo
element in document order,
because the parentheses cause (preceding::foo)
to be
parsed as a primary expression in which context
positions are assigned in document order. Similarly,
ancestor::*[1]
returns the nearest ancestor element,
because the ancestor
axis is a reverse axis, whereas
(ancestor::*)[1]
returns the root element (first
ancestor in document order).
The fact that a reverse-axis step assigns context positions in reverse document order for the purpose of evaluating predicates does not alter the fact that the final result of the step (when in ordered mode) is always in document order.
This section provides a number of examples of path expressions in which the axis is explicitly specified in each step. The syntax used in these examples is called the unabbreviated syntax. In many common cases, it is possible to write path expressions more concisely using an abbreviated syntax, as explained in 3.3.4 Abbreviated Syntax.
child::para
selects the para
element
children of the context node
child::*
selects all element children of the
context node
child::text()
selects all text node children of the
context node
child::node()
selects all the children of the
context node. Note that no attribute nodes are returned, because
attributes are not children.
attribute::name
selects the name
attribute of the context node
attribute::*
selects all the attributes of the
context node
parent::node()
selects the parent of the context
node. If the context node is an attribute node, this expression
returns the element node (if any) to which the attribute node is
attached.
descendant::para
selects the para
element descendants of the context node
ancestor::div
selects all div
ancestors of the context node
ancestor-or-self::div
selects the div
ancestors of the context node and, if the context node is a
div
element, the context node as well
descendant-or-self::para
selects the
para
element descendants of the context node and, if
the context node is a para
element, the context node
as well
self::para
selects the context node if it is a
para
element, and otherwise returns an empty
sequence
child::chapter/descendant::para
selects the
para
element descendants of the chapter
element children of the context node
child::*/child::para
selects all para
grandchildren of the context node
/
selects the root of the tree that contains the
context node, but raises a dynamic error if this root is not a
document node
/descendant::para
selects all the para
elements in the same document as the context node
/descendant::list/child::member
selects all the
member
elements that have a list
parent
and that are in the same document as the context node
child::para[fn:position() = 1]
selects the first
para
child of the context node
child::para[fn:position() = fn:last()]
selects the
last para
child of the context node
child::para[fn:position() = fn:last()-1]
selects
the last but one para
child of the context node
child::para[fn:position() > 1]
selects all the
para
children of the context node other than the first
para
child of the context node
following-sibling::chapter[fn:position() = 1]
selects the next chapter
sibling of the context
node
preceding-sibling::chapter[fn:position() = 1]
selects the previous chapter
sibling of the context
node
/descendant::figure[fn:position() = 42]
selects the
forty-second figure
element in the document containing
the context node
/child::book/child::chapter[fn:position() =
5]/child::section[fn:position() = 2]
selects the second
section
of the fifth chapter
of the
book
whose parent is the document node that contains
the context node
child::para[attribute::type eq "warning"]
selects
all para
children of the context node that have a
type
attribute with value warning
child::para[attribute::type eq 'warning'][fn:position() =
5]
selects the fifth para
child of the context
node that has a type
attribute with value
warning
child::para[fn:position() = 5][attribute::type eq
"warning"]
selects the fifth para
child of the
context node if that child has a type
attribute with
value warning
child::chapter[child::title = 'Introduction']
selects the chapter
children of the context node that
have one or more title
children whose typed value is equal to
the string Introduction
child::chapter[child::title]
selects the
chapter
children of the context node that have one or
more title
children
child::*[self::chapter or self::appendix]
selects
the chapter
and appendix
children of the
context node
child::*[self::chapter or self::appendix][fn:position() =
fn:last()]
selects the last chapter
or
appendix
child of the context node
[110] | AbbrevForwardStep |
::= | "@"? NodeTest |
[113] | AbbrevReverseStep |
::= | ".." |
The abbreviated syntax permits the following abbreviations:
The attribute axis attribute::
can be abbreviated
by @
. For example, a path expression
para[@type="warning"]
is short for
child::para[attribute::type="warning"]
and so selects
para
children with a type
attribute with
value equal to warning
.
If the axis name is omitted from an axis step, the default axis is
child
, with two exceptions: if the axis step contains
an AttributeTest or
SchemaAttributeTest
then the default axis is attribute
; if the axis step
contains namespace-node()
then the default axis is
namespace
.
Note:
In an implementation that does not support the namespace axis, an attempt to access it always raises an error. Thus, an XQuery implementation will always raise an error in this case, since XQuery does not support the namespace axis. The namespace axis is deprecated as of XPath 2.0, but required in some languages that use XPath, including XSLT.
For example, the path expression section/para
is an
abbreviation for child::section/child::para
, and the
path expression section/@id
is an abbreviation for
child::section/attribute::id
. Similarly,
section/attribute(id)
is an abbreviation for
child::section/attribute::attribute(id)
. Note that the
latter expression contains both an axis specification and a
node test.
Each non-initial occurrence of //
is effectively
replaced by /descendant-or-self::node()/
during
processing of a path expression. For example,
div1//para
is short for
child::div1/descendant-or-self::node()/child::para
and
so will select all para
descendants of
div1
children.
Note:
The path expression //para[1]
does not
mean the same as the path expression
/descendant::para[1]
. The latter selects the first
descendant para
element; the former selects all
descendant para
elements that are the first
para
children of their respective parents.
A step consisting of ..
is short for
parent::node()
. For example, ../title
is
short for parent::node()/child::title
and so will
select the title
children of the parent of the context
node.
Note:
The expression .
, known as a context item
expression, is a primary expression, and is described
in 3.1.4 Context Item
Expression.
Here are some examples of path expressions that use the abbreviated syntax:
para
selects the para
element children
of the context node
*
selects all element children of the context
node
text()
selects all text node children of the
context node
@name
selects the name
attribute of
the context node
@*
selects all the attributes of the context
node
para[1]
selects the first para
child
of the context node
para[fn:last()]
selects the last para
child of the context node
*/para
selects all para
grandchildren
of the context node
/book/chapter[5]/section[2]
selects the second
section
of the fifth chapter
of the
book
whose parent is the document node that contains
the context node
chapter//para
selects the para
element
descendants of the chapter
element children of the
context node
//para
selects all the para
descendants of the root document node and thus selects all
para
elements in the same document as the context
node
//@version
selects all the version
attribute nodes that are in the same document as the context
node
//list/member
selects all the member
elements in the same document as the context node that have a
list
parent
.//para
selects the para
element
descendants of the context node
..
selects the parent of the context node
../@lang
selects the lang
attribute of
the parent of the context node
para[@type="warning"]
selects all para
children of the context node that have a type
attribute with value warning
para[@type="warning"][5]
selects the fifth
para
child of the context node that has a
type
attribute with value warning
para[5][@type="warning"]
selects the fifth
para
child of the context node if that child has a
type
attribute with value warning
chapter[title="Introduction"]
selects the
chapter
children of the context node that have one or
more title
children whose typed value is equal to the string
Introduction
chapter[title]
selects the chapter
children of the context node that have one or more
title
children
employee[@secretary and @assistant]
selects all the
employee
children of the context node that have both a
secretary
attribute and an assistant
attribute
book/(chapter|appendix)/section
selects every
section
element that has a parent that is either a
chapter
or an appendix
element, that in
turn is a child of a book
element that is a child of
the context node.
If E
is any expression that returns a sequence of
nodes, then the expression E/.
returns the same nodes
in document
order, with duplicates eliminated based on node identity.
XQuery 3.0 supports operators to construct, filter, and combine
sequences of items. Sequences are never nested—for
example, combining the values 1
, (2, 3)
,
and ( )
into a single sequence results in the sequence
(1, 2, 3)
.
[39] | Expr |
::= | ExprSingle (","
ExprSingle)* |
[85] | RangeExpr |
::= | AdditiveExpr (
"to" AdditiveExpr
)? |
[Definition: One way to construct a sequence is by using the comma operator, which evaluates each of its operands and concatenates the resulting sequences, in order, into a single result sequence.] Empty parentheses can be used to denote an empty sequence.
A sequence may contain duplicate items, but a sequence is never an item in another sequence. When a new sequence is created by concatenating two or more input sequences, the new sequence contains all the items of the input sequences and its length is the sum of the lengths of the input sequences.
Note:
In places where the grammar calls for ExprSingle, such as the arguments of a function call, any expression that contains a top-level comma operator must be enclosed in parentheses.
Here are some examples of expressions that construct sequences:
The result of this expression is a sequence of five integers:
(10, 1, 2, 3, 4)
This expression combines four sequences of length one, two,
zero, and two, respectively, into a single sequence of length five.
The result of this expression is the sequence 10, 1, 2, 3,
4
.
(10, (1, 2), (), (3, 4))
The result of this expression is a sequence containing all
salary
children of the context node followed by all
bonus
children.
(salary, bonus)
Assuming that $price
is bound to the value
10.50
, the result of this expression is the sequence
10.50, 10.50
.
($price, $price)
A range expression can be used to construct a sequence of
consecutive integers. Each of the operands of the to
operator is converted as though it was an argument of a function
with the expected parameter type xs:integer?
. If
either operand is an empty sequence, or if the integer derived from
the first operand is greater than the integer derived from the
second operand, the result of the range expression is an empty
sequence. If the two operands convert to the same integer, the
result of the range expression is that integer. Otherwise, the
result is a sequence containing the two integer operands and every
integer between the two operands, in increasing order.
This example uses a range expression as one operand in
constructing a sequence. It evaluates to the sequence 10, 1,
2, 3, 4
.
(10, 1 to 4)
This example constructs a sequence of length one containing the
single integer 10
.
10 to 10
The result of this example is a sequence of length zero.
15 to 10
This example uses the fn:reverse
function to
construct a sequence of six integers in decreasing order. It
evaluates to the sequence 15, 14, 13, 12, 11, 10
.
fn:reverse(10 to 15)
[88] | UnionExpr |
::= | IntersectExceptExpr (
("union" | "|") IntersectExceptExpr
)* |
[89] | IntersectExceptExpr |
::= | InstanceofExpr
( ("intersect" | "except") InstanceofExpr )* |
XQuery 3.0 provides the following operators for combining sequences of nodes:
The union
and |
operators are
equivalent. They take two node sequences as operands and return a
sequence containing all the nodes that occur in either of the
operands.
The intersect
operator takes two node sequences as
operands and returns a sequence containing all the nodes that occur
in both operands.
The except
operator takes two node sequences as
operands and returns a sequence containing all the nodes that occur
in the first operand but not in the second operand.
All these operators eliminate duplicate nodes from their result
sequences based on node identity. If ordering mode is
ordered
, the resulting sequence is returned in
document
order; otherwise it is returned in implementation-dependent
order.
If an operand of union
, intersect
, or
except
contains an item that is not a node, a
type error is
raised [err:XPTY0004].
If an IntersectExceptExpr contains more than two InstanceofExprs, they are grouped from left to right. With a UnionExpr, it makes no difference how operands are grouped, the results are the same.
Here are some examples of expressions that combine sequences.
Assume the existence of three element nodes that we will refer to
by symbolic names A, B, and C. Assume that
ordering mode
is ordered
. Assume that the variables
$seq1
, $seq2
and $seq3
are
bound to the following sequences of these nodes:
$seq1
is bound to (A, B)
$seq2
is bound to (A, B)
$seq3
is bound to (B, C)
Then:
$seq1 union $seq2
evaluates to the sequence (A,
B).
$seq2 union $seq3
evaluates to the sequence (A, B,
C).
$seq1 intersect $seq2
evaluates to the sequence (A,
B).
$seq2 intersect $seq3
evaluates to the sequence
containing B only.
$seq1 except $seq2
evaluates to the empty
sequence.
$seq2 except $seq3
evaluates to the sequence
containing A only.
In addition to the sequence operators described here, [XQuery and XPath Functions and Operators 3.0] includes functions for indexed access to items or sub-sequences of a sequence, for indexed insertion or removal of items in a sequence, and for removing duplicate items from a sequence.
XQuery 3.0 provides arithmetic operators for addition, subtraction, multiplication, division, and modulus, in their usual binary and unary forms.
[86] | AdditiveExpr |
::= | MultiplicativeExpr ( ("+" |
"-") MultiplicativeExpr
)* |
[87] | MultiplicativeExpr |
::= | UnionExpr ( ("*" |
"div" | "idiv" | "mod") UnionExpr )* |
[94] | UnaryExpr |
::= | ("-" | "+")* ValueExpr |
[95] | ValueExpr |
::= | ValidateExpr |
PathExpr | ExtensionExpr |
A subtraction operator must be preceded by whitespace if it
could otherwise be interpreted as part of the previous token. For
example, a-b
will be interpreted as a name, but
a - b
and a -b
will be interpreted as
arithmetic expressions. (See A.2.4
Whitespace Rules for further details on whitespace
handling.)
If an AdditiveExpr contains more than two MultiplicativeExprs, they are grouped from left to right. So, for instance,
A - B + C - D
is equivalent to
((A - B) + C) - D
Similarly, the operands of a MultiplicativeExpr are grouped from left to right.
The first step in evaluating an arithmetic expression is to evaluate its operands. The order in which the operands are evaluated is implementation-dependent.
Each operand is evaluated by applying the following steps, in order:
Atomization is applied to the operand. The result of this operation is called the atomized operand.
If the atomized operand is an empty sequence, the result of the arithmetic expression is an empty sequence, and the implementation need not evaluate the other operand or apply the operator. However, an implementation may choose to evaluate the other operand in order to determine whether it raises an error.
If the atomized operand is a sequence of length greater than one, a type error is raised [err:XPTY0004].
If the atomized operand is of type
xs:untypedAtomic
, it is cast to
xs:double
. If the cast fails, a dynamic error is
raised. [err:FORG0001]
After evaluation of the operands, if the types of the operands are a valid combination for the given arithmetic operator, the operator is applied to the operands, resulting in an atomic value or a dynamic error (for example, an error might result from dividing by zero.) The combinations of atomic types that are accepted by the various arithmetic operators, and their respective result types, are listed in B.2 Operator Mapping together with the operator functions that define the semantics of the operator for each type combination, including the dynamic errors that can be raised by the operator. The definitions of the operator functions are found in [XQuery and XPath Functions and Operators 3.0].
If the types of the operands, after evaluation, are not a valid combination for the given operator, according to the rules in B.2 Operator Mapping, a type error is raised [err:XPTY0004].
XQuery 3.0 supports two division operators named
div
and idiv
. Each of these operators
accepts two operands of any numeric type. As described in [XQuery and XPath Functions and Operators
3.0], $arg1 idiv $arg2
is equivalent to
($arg1 div $arg2) cast as xs:integer?
except for error
cases.
Here are some examples of arithmetic expressions:
The first expression below returns the xs:decimal
value -1.5
, and the second expression returns the
xs:integer
value -1
:
-3 div 2 -3 idiv 2
Subtraction of two date values results in a value of type
xs:dayTimeDuration
:
$emp/hiredate - $emp/birthdate
This example illustrates the difference between a subtraction operator and a hyphen:
$unit-price - $unit-discount
Unary operators have higher precedence than binary operators, subject of course to the use of parentheses. Therefore, the following two examples have different meanings:
-$bellcost + $whistlecost -($bellcost + $whistlecost)
Note:
Multiple consecutive unary arithmetic operators are permitted by XQuery 3.0 for compatibility with [XML Path Language (XPath) Version 1.0].
Comparison expressions allow two values to be compared. XQuery 3.0 provides three kinds of comparison expressions, called value comparisons, general comparisons, and node comparisons.
[84] | ComparisonExpr |
::= | RangeExpr (
(ValueComp |
[97] | ValueComp |
::= | "eq" | "ne" | "lt" | "le" | "gt" | "ge" |
[96] | GeneralComp |
::= | "=" | "!=" | "<" | "<=" | ">" |
">=" |
[98] | NodeComp |
::= | "is" | "<<" | ">>" |
The value comparison operators are eq
,
ne
, lt
, le
, gt
,
and ge
. Value comparisons are used for comparing
single values.
The first step in evaluating a value comparison is to evaluate its operands. The order in which the operands are evaluated is implementation-dependent. Each operand is evaluated by applying the following steps, in order:
Atomization is applied to the operand. The result of this operation is called the atomized operand.
If the atomized operand is an empty sequence, the result of the value comparison is an empty sequence, and the implementation need not evaluate the other operand or apply the operator. However, an implementation may choose to evaluate the other operand in order to determine whether it raises an error.
If the atomized operand is a sequence of length greater than one, a type error is raised [err:XPTY0004].
If the atomized operand is of type
xs:untypedAtomic
, it is cast to
xs:string
.
Note:
The purpose of this rule is to make value comparisons
transitive. Users should be aware that the general comparison
operators have a different rule for casting of
xs:untypedAtomic
operands. Users should also be aware
that transitivity of value comparisons may be compromised by loss
of precision during type conversion (for example, two
xs:integer
values that differ slightly may both be
considered equal to the same xs:float
value because
xs:float
has less precision than
xs:integer
).
Next, if possible, the two operands are converted to their least
common type by a combination of type promotion and subtype
substitution. For example, if the operands are of type
hatsize
(derived from xs:integer
) and
shoesize
(derived from xs:float
), their
least common type is xs:float
.
Finally, if the types of the operands are a valid combination for the given operator, the operator is applied to the operands. The combinations of atomic types that are accepted by the various value comparison operators, and their respective result types, are listed in B.2 Operator Mapping together with the operator functions that define the semantics of the operator for each type combination. The definitions of the operator functions are found in [XQuery and XPath Functions and Operators 3.0].
Informally, if both atomized operands consist of exactly one
atomic value, then the result of the comparison is
true
if the value of the first operand is (equal, not
equal, less than, less than or equal, greater than, greater than or
equal) to the value of the second operand; otherwise the result of
the comparison is false
.
If the types of the operands, after evaluation, are not a valid combination for the given operator, according to the rules in B.2 Operator Mapping, a type error is raised [err:XPTY0004].
Here are some examples of value comparisons:
The following comparison atomizes the node(s) that are returned
by the expression $book/author
. The comparison is true
only if the result of atomization is the value "Kennedy" as an
instance of xs:string
or
xs:untypedAtomic
. If the result of atomization is an
empty sequence, the result of the comparison is an empty sequence.
If the result of atomization is a sequence containing more than one
value, a type error
is raised [err:XPTY0004].
$book1/author eq "Kennedy"
The following path expression contains a predicate that
selects products whose weight is greater than 100. For any product
that does not have a weight
subelement, the value of
the predicate is the empty sequence, and the product is not
selected. This example assumes that weight
is a
validated element with a numeric type.
//product[weight gt 100]
The following comparisons are true because, in each case, the two constructed nodes have the same value after atomization, even though they have different identities and/or names:
<a>5</a> eq <a>5</a>
<a>5</a> eq <b>5</b>
The following comparison is true if my:hatsize
and
my:shoesize
are both user-defined types that are
derived by restriction from a primitive numeric type:
my:hatsize(5) eq my:shoesize(5)
The following comparison is true. The eq
operator
compares two QNames by performing codepoint-comparisons of their
namespace URIs and their local names, ignoring their namespace
prefixes.
fn:QName("http://example.com/ns1", "this:color") eq fn:QName("http://example.com/ns1", "that:color")
The general comparison operators are =
,
!=
, <
, <=
,
>
, and >=
. General comparisons are
existentially quantified comparisons that may be applied to operand
sequences of any length. The result of a general comparison that
does not raise an error is always true
or
false
.
A general comparison is evaluated by applying the following rules, in order:
Atomization is applied to each operand. After atomization, each operand is a sequence of atomic values.
The result of the comparison is true
if and only if
there is a pair of atomic values, one in the first operand sequence
and the other in the second operand sequence, that have the
required magnitude relationship. Otherwise the result of the
comparison is false
. The magnitude relationship
between two atomic values is determined by applying the following
rules. If a cast
operation called for by these rules
is not successful, a dynamic error is raised. [err:FORG0001]
Note:
The purpose of these rules is to preserve compatibility with
XPath 1.0, in which (for example) x < 17
is a
numeric comparison if x
is an untyped value. Users
should be aware that the value comparison operators have different
rules for casting of xs:untypedAtomic
operands.
If both atomic values are instances of
xs:untypedAtomic
, then the values are cast to the type
xs:string
.
If exactly one of the atomic values is an instance of
xs:untypedAtomic
, it is cast to a type depending on
the other value's dynamic type T according to the following rules,
in which V denotes the value to be cast:
If T is a numeric type or is derived from a numeric type, then V
is cast to xs:double
.
If T is xs:dayTimeDuration
or is derived from
xs:dayTimeDuration
, then V is cast to
xs:dayTimeDuration
.
If T is xs:yearMonthDuration
or is derived from
xs:yearMonthDuration
, then V is cast to
xs:yearMonthDuration
.
In all other cases, V is cast to the primitive base type of T.
Note:
The special treatment of the duration types is required to avoid
errors that may arise when comparing the primitive type
xs:duration
with any duration type.
After performing the conversions described above, the atomic
values are compared using one of the value comparison operators
eq
, ne
, lt
, le
,
gt
, or ge
, depending on whether the
general comparison operator was =
, !=
,
<
, <=
, >
, or
>=
. The values have the required magnitude
relationship if and only if the result of this value comparison
is true
.
When evaluating a general comparison in which either operand is
a sequence of items, an implementation may return true
as soon as it finds an item in the first operand and an item in the
second operand that have the required magnitude
relationship. Similarly, a general comparison may raise a
dynamic error
as soon as it encounters an error in evaluating either operand, or
in comparing a pair of items from the two operands. As a result of
these rules, the result of a general comparison is not
deterministic in the presence of errors.
Here are some examples of general comparisons:
The following comparison is true if the typed value of any author
subelement of $book1
is "Kennedy" as an instance of
xs:string
or xs:untypedAtomic
:
$book1/author = "Kennedy"
The following example contains three general comparisons. The
value of the first two comparisons is true
, and the
value of the third comparison is false
. This example
illustrates the fact that general comparisons are not
transitive.
(1, 2) = (2, 3) (2, 3) = (3, 4) (1, 2) = (3, 4)
The following example contains two general comparisons, both of
which are true
. This example illustrates the fact that
the =
and !=
operators are not inverses
of each other.
(1, 2) = (2, 3) (1, 2) != (2, 3)
Suppose that $a
, $b
, and
$c
are bound to element nodes with type annotation
xs:untypedAtomic
, with string values "1
",
"2
", and "2.0
" respectively. Then
($a, $b) = ($c, 3.0)
returns false
,
because $b
and $c
are compared as
strings. However, ($a, $b) = ($c, 2.0)
returns
true
, because $b
and 2.0
are
compared as numbers.
Node comparisons are used to compare two nodes, by their identity or by their document order. The result of a node comparison is defined by the following rules:
The operands of a node comparison are evaluated in implementation-dependent order.
If either operand is an empty sequence, the result of the comparison is an empty sequence, and the implementation need not evaluate the other operand or apply the operator. However, an implementation may choose to evaluate the other operand in order to determine whether it raises an error.
Each operand must be either a single node or an empty sequence; otherwise a type error is raised [err:XPTY0004].
A comparison with the is
operator is
true
if the two operand nodes have the same identity,
and are thus the same node; otherwise it is false
. See
[XQuery and XPath Data Model (XDM)
3.0] for a definition of node identity.
A comparison with the <<
operator returns
true
if the left operand node precedes the right
operand node in document order; otherwise it returns
false
.
A comparison with the >>
operator returns
true
if the left operand node follows the right
operand node in document order; otherwise it returns
false
.
Here are some examples of node comparisons:
The following comparison is true only if the left and right sides each evaluate to exactly the same single node:
/books/book[isbn="1558604820"] is /books/book[call="QA76.9 C3845"]
The following comparison is false because each constructed node has its own identity:
<a>5</a> is <a>5</a>
The following comparison is true only if the node identified by the left side occurs before the node identified by the right side in document order:
/transactions/purchase[parcel="28-451"] << /transactions/sale[parcel="33-870"]
A logical expression is either an and-expression
or an or-expression. If a logical expression does not raise
an error, its value is always one of the boolean values
true
or false
.
[82] | OrExpr |
::= | AndExpr ( "or"
AndExpr )* |
[83] | AndExpr |
::= | ComparisonExpr
( "and" ComparisonExpr
)* |
The first step in evaluating a logical expression is to find the effective boolean value of each of its operands (see 2.4.3 Effective Boolean Value).
The value of an and-expression is determined by the effective boolean values (EBV's) of its operands, as shown in the following table:
AND: | EBV2 = true |
EBV2 = false |
error in EBV2 |
EBV1 = true |
true |
false |
error |
EBV1 = false |
false |
false |
either false or
error |
error in EBV1 | error | either false or
error |
error |
The value of an or-expression is determined by the effective boolean values (EBV's) of its operands, as shown in the following table:
OR: | EBV2 = true |
EBV2 = false |
error in EBV2 |
EBV1 = true |
true |
true |
either true or
error |
EBV1 = false |
true |
false |
error |
error in EBV1 | either true or
error |
error | error |
The order in which the operands of a
logical expression are evaluated is implementation-dependent. The
tables above are defined in such a way that an or-expression
can return true
if the first expression evaluated is
true, and it can raise an error if evaluation of the first
expression raises an error. Similarly, an and-expression can return
false
if the first expression evaluated is false, and
it can raise an error if evaluation of the first expression raises
an error. As a result of these rules, a logical expression is not
deterministic in the presence of errors, as illustrated in the
examples below.
Here are some examples of logical expressions:
The following expressions return true
:
1 eq 1 and 2 eq 2
1 eq 1 or 2 eq 3
The following expression may return either false
or
raise a dynamic
error:
1 eq 2 and 3 idiv 0 = 1
The following expression may return either true
or
raise a dynamic
error:
1 eq 1 or 3 idiv 0 = 1
The following expression must raise a dynamic error:
1 eq 1 and 3 idiv 0 = 1
In addition to and- and or-expressions, XQuery 3.0 provides a
function named fn:not
that takes a general sequence as
parameter and returns a boolean value. The fn:not
function is defined in [XQuery and
XPath Functions and Operators 3.0]. The fn:not
function reduces its parameter to an effective boolean
value. It then returns true
if the effective
boolean value of its parameter is false
, and
false
if the effective boolean value of its parameter
is true
. If an error is encountered in finding the
effective boolean value of its operand, fn:not
raises
the same error.
XQuery provides constructors that can create XML structures within a query. Constructors are provided for element, attribute, document, text, comment, and processing instruction nodes. Two kinds of constructors are provided: direct constructors, which use an XML-like notation, and computed constructors, which use a notation based on enclosed expressions.
This section contains a conceptual description of the semantics of various kinds of constructor expressions. An XQuery implementation is free to use any implementation technique that produces the same result as the processing steps described in this section.
An element constructor creates an element node. [Definition: A direct element
constructor is a form of element constructor in which the name
of the constructed element is a constant.] Direct element
constructors are based on standard XML notation. For example, the
following expression is a direct element constructor that creates a
book
element containing an attribute and some nested
elements:
<book isbn="isbn-0060229357"> <title>Harold and the Purple Crayon</title> <author> <first>Crockett</first> <last>Johnson</last> </author> </book>
If the element name in a direct element constructor has a
namespace prefix, the namespace prefix is resolved to a namespace
URI using the statically known namespaces. If the
element name has no namespace prefix, it is implicitly qualified by
the default element/type namespace. Note that
both the statically known namespaces and the default element/type
namespace may be affected by namespace declaration attributes
found inside the element constructor. The namespace prefix of the
element name is retained after expansion of the lexical QName , as described
in [XQuery and XPath Data Model (XDM)
3.0]. The resulting expanded QName becomes the
node-name
property of the constructed element
node.
In a direct element constructor, the name used in the end tag must exactly match the name used in the corresponding start tag, including its prefix or absence of a prefix [err:XQST0118].
In a direct element constructor, curly braces { } delimit enclosed expressions, distinguishing them from literal text. Enclosed expressions are evaluated and replaced by their value, as illustrated by the following example:
<example> <p> Here is a query. </p> <eg> $b/title </eg> <p> Here is the result of the query. </p> <eg>{ $b/title }</eg> </example>
The above query might generate the following result (whitespace has been added for readability to this result and other result examples in this document):
<example> <p> Here is a query. </p> <eg> $b/title </eg> <p> Here is the result of the query. </p> <eg><title>Harold and the Purple Crayon</title></eg> </example>
Since XQuery uses curly braces to denote enclosed expressions,
some convention is needed to denote a curly brace used as an
ordinary character. For this purpose, a pair of identical curly
brace characters within the content of an element or attribute are
interpreted by XQuery as a single curly brace character (that is,
the pair "{{
" represents the character
"{
" and the pair "}}
" represents the
character "}
".) Alternatively, the character
references {
and }
can be used to denote curly brace characters. A single left curly
brace ("{
") is interpreted as the beginning delimiter
for an enclosed expression. A single right curly brace
("}
") without a matching left curly brace is treated
as a static
error [err:XPST0003].
The result of an element constructor is a new element node, with its own node identity. All the attribute and descendant nodes of the new element node are also new nodes with their own identities, even if they are copies of existing nodes.
The start tag of a direct element constructor may contain one or more attributes. As in XML, each attribute is specified by a name and a value. In a direct element constructor, the name of each attribute is specified by a constant lexical QName, and the value of the attribute is specified by a string of characters enclosed in single or double quotes. As in the main content of the element constructor, an attribute value may contain expressions enclosed in curly braces, which are evaluated and replaced by their value during processing of the element constructor.
Each attribute in a direct element constructor creates a new attribute node, with its own node identity, whose parent is the constructed element node. However, note that namespace declaration attributes (see 3.8.1.2 Namespace Declaration Attributes) do not create attribute nodes.
If an attribute name has a namespace prefix, the prefix is
resolved to a namespace URI using the statically known namespaces. If the
attribute name has no namespace prefix, the attribute is in no
namespace. Note that the statically known namespaces used in
resolving an attribute name may be affected by namespace declaration attributes that
are found inside the same element constructor. The namespace prefix
of the attribute name is retained after expansion of the lexical QName, as described in
[XQuery and XPath Data Model (XDM)
3.0]. The resulting expanded QName becomes the
node-name
property of the constructed attribute
node.
If the attributes in a direct element constructor do not have
distinct expanded QNames as their respective
node-name
properties, a static error is raised [err:XQST0040].
Conceptually, an attribute (other than a namespace declaration attribute) in a direct element constructor is processed by the following steps:
Each consecutive sequence of literal characters in the attribute content is processed as a string literal containing those characters, with the following exceptions:
Each occurrence of two consecutive {
characters is
replaced by a single {
character.
Each occurrence of two consecutive }
characters is
replaced by a single }
character.
Each occurrence of EscapeQuot is replaced by a single
"
character.
Each occurrence of EscapeApos is replaced by a single
'
character.
Attribute value normalization is then applied to normalize whitespace and expand character references and predefined entity references. An XQuery processor that supports XML 1.0 uses the rules for attribute value normalization in Section 3.3.3 of [XML 1.0]; an XQuery processor that supports XML 1.1 uses the rules for attribute value normalization in Section 3.3.3 of [XML 1.1]. In either case, the normalization rules are applied as though the type of the attribute were CDATA (leading and trailing whitespace characters are not stripped.) The choice between XML 1.0 and XML 1.1 rules is implementation-defined.
Each enclosed expression is converted to a string as follows:
Atomization is applied to the value of the enclosed expression, converting it to a sequence of atomic values.
If the result of atomization is an empty sequence, the result is the zero-length string. Otherwise, each atomic value in the atomized sequence is cast into a string.
The individual strings resulting from the previous step are merged into a single string by concatenating them with a single space character between each pair.
Adjacent strings resulting from the above steps are concatenated
with no intervening blanks. The resulting string becomes the
string-value
property of the attribute node. The
attribute node is given a type annotation of
xs:untypedAtomic
(this type annotation may change if
the parent element is validated). The typed-value
property of the attribute node is the same as its
string-value
, as an instance of
xs:untypedAtomic
.
The parent
property of the attribute node is set to
the element node constructed by the direct element constructor that
contains this attribute.
If the attribute name is xml:id
, then
xml:id
processing is performed as defined in [XML ID]. This ensures that the attribute has the type
xs:ID
and that its value is properly normalized. If an
error is encountered during xml:id
processing, an
implementation may raise a dynamic error [err:XQDY0091].
If the attribute name is xml:id
, the
is-id
property of the resulting attribute node is set
to true
; otherwise the is-id
property is
set to false
. The is-idrefs
property of
the attribute node is unconditionally set to
false
.
Example:
<shoe size="7"/>
The string value of the size
attribute is
"7
".
Example:
<shoe size="{7}"/>
The string value of the size
attribute is
"7
".
Example:
<shoe size="{()}"/>
The string value of the size
attribute is the
zero-length string.
Example:
<chapter ref="[{1, 5 to 7, 9}]"/>
The string value of the ref
attribute is "[1
5 6 7 9]
".
Example:
<shoe size="As big as {$hat/@size}"/>
The string value of the size
attribute is the
string "As big as
", concatenated with the string
value of the node denoted by the expression
$hat/@size
.
The names of a constructed element and its attributes may be lexical QNames that include namespace prefixes. Namespace prefixes can be bound to namespaces in the Prolog or by namespace declaration attributes. It is a static error to use a namespace prefix that has not been bound to a namespace [err:XPST0081].
[Definition: A
namespace declaration attribute is used inside a direct
element constructor. Its purpose is to bind a namespace prefix or
to set the default element/type namespace for the
constructed element node, including its attributes.] Syntactically,
a namespace declaration attribute has the form of an attribute with
namespace prefix xmlns
, or with name
xmlns
and no namespace prefix. All the namespace
declaration attributes of a given element must have distinct names
[err:XQST0071].
Each namespace declaration attribute is processed as follows:
The value of the namespace declaration attribute (a DirAttributeValue) is
processed as follows. If the DirAttributeValue contains an
EnclosedExpr, a static
error is raised [err:XQST0022]. Otherwise, it is processed as
described in rule 1 of 3.8.1.1
Attributes. An implementation MAY raise a static error
[err:XQST0046] if
the resulting value is of nonzero length and is not in the lexical
space of xs:anyURI
. The resulting value is used as the
namespace URI in the following rules.
If the prefix of the attribute name is xmlns
, then
the local part of the attribute name is interpreted as a namespace
prefix. This prefix and the namespace URI are added to the
statically known namespaces of the
constructor expression (overriding any existing binding of the
given prefix), and are also added as a namespace binding to the
in-scope namespaces of the
constructed element. If the namespace URI is a zero-length string
and the implementation supports [XML Names
1.1], any existing namespace binding for the given prefix is
removed from the in-scope namespaces of the
constructed element and from the statically known namespaces of the
constructor expression. If the namespace URI is a zero-length
string and the implementation does not support [XML Names 1.1], a static error is raised
[err:XQST0085]. It
is implementation-defined whether an
implementation supports [XML Names] or
[XML Names 1.1].
If the name of the namespace declaration attribute is
xmlns
with no prefix, then the namespace URI specifies
the default element/type namespace of the
constructor expression (overriding any existing default), and is
added (with no prefix) to the in-scope namespaces of the
constructed element (overriding any existing namespace binding with
no prefix). If the namespace URI is a zero-length string, the
default element/type namespace of the
constructor expression is set to absentDM30,
and any no-prefix namespace binding is removed from the in-scope
namespaces of the constructed element.
It is a static error [err:XQST0070] if a namespace declaration attribute attempts to do any of the following:
Bind the prefix xml
to some namespace URI other
than http://www.w3.org/XML/1998/namespace
.
Bind a prefix other than xml
to the namespace URI
http://www.w3.org/XML/1998/namespace
.
Bind the prefix xmlns
to any namespace URI.
Bind a prefix to the namespace URI
http://www.w3.org/2000/xmlns/
.
A namespace declaration attribute does not cause an attribute node to be created.
The following examples illustrate namespace declaration attributes:
In this element constructor, a namespace declaration attribute
is used to set the default element/type namespace to
http://example.org/animals
:
<cat xmlns = "http://example.org/animals"> <breed>Persian</breed> </cat>
In this element constructor, namespace declaration attributes
are used to bind the namespace prefixes metric
and
english
:
<box xmlns:metric = "http://example.org/metric/units" xmlns:english = "http://example.org/english/units"> <height> <metric:meters>3</metric:meters> </height> <width> <english:feet>6</english:feet> </width> <depth> <english:inches>18</english:inches> </depth> </box>
The part of a direct element constructor between the start tag and the end tag is called the content of the element constructor. This content may consist of text characters (parsed as ElementContentChar), nested direct constructors, CDataSections, character and predefined entity references, and expressions enclosed in curly braces. In general, the value of an enclosed expression may be any sequence of nodes and/or atomic values. Enclosed expressions can be used in the content of an element constructor to compute both the content and the attributes of the constructed node.
Conceptually, the content of an element constructor is processed as follows:
The content is evaluated to produce a sequence of nodes called the content sequence, as follows:
If the boundary-space policy in the
static
context is strip
, boundary whitespace is
identified and deleted (see 3.8.1.4
Boundary Whitespace for a definition of boundary
whitespace.)
Predefined entity references
and character references are expanded
into their referenced strings, as described in 3.1.1 Literals. Characters inside a
CDataSection, including
special characters such as <
and
&
, are treated as literal characters rather than
as markup characters (except for the sequence ]]>
,
which terminates the CDataSection).
Each consecutive sequence of literal characters evaluates to a single text node containing the characters.
Each nested direct constructor is evaluated according to the rules in 3.8.1 Direct Element Constructors or 3.8.2 Other Direct Constructors, resulting in a new element, comment, or processing instruction node. Then:
The parent
property of the resulting node is then
set to the newly constructed element node.
The base-uri
property of the resulting node, and of
each of its descendants, is set to be the same as that of its new
parent, unless it (the child node) has an xml:base
attribute, in which case its base-uri
property is set
to the value of that attribute, resolved (if it is relative) against
the base-uri
property of its new parent node.
Enclosed expressions are evaluated as follows:
If an enclosed expression returns a function itemDM30, a type error is raised [err:XQTY0105].
For each adjacent sequence of one or more atomic values returned by an enclosed expression, a new text node is constructed, containing the result of casting each atomic value to a string, with a single space character inserted between adjacent values.
Note:
The insertion of blank characters between adjacent values applies even if one or both of the values is a zero-length string.
For each node returned by an enclosed expression, a new copy is made of the given node and all nodes that have the given node as an ancestor, collectively referred to as copied nodes. The properties of the copied nodes are as follows:
Each copied node receives a new node identity.
The parent
, children
, and
attributes
properties of the copied nodes are set so
as to preserve their inter-node relationships. For the topmost node
(the node directly returned by the enclosed expression), the
parent
property is set to the node constructed by this
constructor.
If construction mode in the static context is
strip
:
If the copied node is an element node, its type annotation is
set to xs:untyped
. Its nilled
,
is-id
, and is-idrefs
properties are set
to false
.
If the copied node is an attribute node, its
type-name
property is set to
xs:untypedAtomic
. Its is-idrefs
property
is set to false
. Its is-id
property is
set to true
if the qualified name of the attribute
node is xml:id
; otherwise it is set to
false
.
The string-value
of each copied element and
attribute node remains unchanged, and its typed-value
becomes equal to its string-value
as an instance of
xs:untypedAtomic
.
Note:
Implementations that store only the typed value of a node are required at this point to convert the typed value to a string form.
On the other hand, if construction mode in the static context is
preserve
, the type-name
,
nilled
, string-value
,
typed-value
, is-id
, and
is-idrefs
properties of the copied nodes are
preserved.
The in-scope-namespaces
property of a copied
element node is determined by the following rules. In applying
these rules, the default namespace or absence of a default
namespace is treated like any other namespace binding:
If copy-namespaces mode specifies
preserve
, all in-scope-namespaces of the original
element are retained in the new copy. If copy-namespaces mode specifies
no-preserve
, the new copy retains only those in-scope
namespaces of the original element that are used in the names of
the element and its attributes.
If copy-namespaces mode specifies
inherit
, the copied node inherits all the in-scope
namespaces of the constructed node, augmented and overridden by the
in-scope namespaces of the original element that were preserved by
the preceding rule. If copy-namespaces mode specifies
no-inherit
, the copied node does not inherit any
in-scope namespaces from the constructed node.
An enclosed expression in the content of an element constructor may cause one or more existing nodes to be copied. Type error [err:XQTY0086] is raised in the following cases:
An element node is copied, and the typed value of the element node or one of its
attributes is namespace-sensitive, and construction
mode is preserve
, and copy-namespaces mode is
no-preserve
.
An attribute node is copied but its parent element node is not
copied, and the typed
value of the copied attribute node is namespace-sensitive, and construction
mode is preserve
.
Note:
The rationale for error [err:XQTY0086] is as follows: It is not possible to preserve the type of a QName without also preserving the namespace binding that defines the prefix of the QName.
When an element or processing instruction node is copied, its
base-uri
property is set to be the same as that of its
new parent, with the following exception: if a copied element node
has an xml:base
attribute, its base-uri
property is set to the value of that attribute, resolved (if it is relative)
against the base-uri
property of the new parent
node.
All other properties of the copied nodes are preserved.
If the content sequence contains a document node, the document node is replaced in the content sequence by its children.
Adjacent text nodes in the content sequence are merged into a single text node by concatenating their contents, with no intervening blanks. After concatenation, any text node whose content is a zero-length string is deleted from the content sequence.
If the content sequence contains an attribute node or a namespace node following a node that is not an attribute node or a namespace node, a type error is raised [err:XQTY0024].
The properties of the newly constructed element node are determined as follows:
node-name
is the expanded QName resulting from resolving
the element name in the start tag, including its original namespace
prefix (if any), as described in 3.8.1 Direct Element
Constructors.
parent
is set to empty.
attributes
consist of all the attributes specified
in the start tag as described in 3.8.1.1 Attributes, together with all
the attribute nodes in the content sequence, in implementation-dependent order.
Note that the parent
property of each of these
attribute nodes has been set to the newly constructed element node.
If two or more attributes have the same node-name
, a
dynamic error
is raised [err:XQDY0025]. If an attribute named
xml:space
has a value other than preserve
or default
, a dynamic error may be raised [err:XQDY0092].
children
consist of all the element, text, comment,
and processing instruction nodes in the content sequence. Note that
the parent
property of each of these nodes has been
set to the newly constructed element node.
base-uri
is set to the following value:
If the constructed node has an attribute named
xml:base
, then the value of this attribute, resolved (if it is
relative) against the Dynamic Base URI.
Otherwise, the Dynamic Base URI.
in-scope-namespaces
consist of all the namespace
bindings resulting from namespace declaration attributes as
described in 3.8.1.2 Namespace
Declaration Attributes, and possibly additional namespace
bindings as described in 3.8.4 In-scope Namespaces of a
Constructed Element.
The nilled
property is false
.
The string-value
property is equal to the
concatenated contents of the text-node descendants in document
order. If there are no text-node descendants, the
string-value
property is a zero-length string.
The typed-value
property is equal to the
string-value
property, as an instance of
xs:untypedAtomic
.
If construction mode in the static context is
strip
, the type-name
property is
xs:untyped
. On the other hand, if construction mode is
preserve
, the type-name
property is
xs:anyType
.
The is-id
and is-idrefs
properties are
set to false
.
Example:
<a>{1}</a>
The constructed element node has one child, a text node
containing the value "1
".
Example:
<a>{1, 2, 3}</a>
The constructed element node has one child, a text node
containing the value "1 2 3
".
Example:
<c>{1}{2}{3}</c>
The constructed element node has one child, a text node
containing the value "123
".
Example:
<b>{1, "2", "3"}</b>
The constructed element node has one child, a text node
containing the value "1 2 3
".
Example:
<fact>I saw 8 cats.</fact>
The constructed element node has one child, a text node
containing the value "I saw 8 cats.
".
Example:
<fact>I saw {5 + 3} cats.</fact>
The constructed element node has one child, a text node
containing the value "I saw 8 cats.
".
Example:
<fact>I saw <howmany>{5 + 3}</howmany> cats.</fact>
The constructed element node has three children: a text node
containing "I saw
", a child element node named
howmany
, and a text node containing "
cats.
". The child element node in turn has a single
text node child containing the value "8
".
In a direct element constructor, whitespace characters may
appear in the content of the constructed element. In some cases,
enclosed expressions and/or nested elements may be separated only
by whitespace characters. For example, in the expression below, the
end-tag </title>
and the start-tag
<author>
are separated by a newline character
and four space characters:
<book isbn="isbn-0060229357"> <title>Harold and the Purple Crayon</title> <author> <first>Crockett</first> <last>Johnson</last> </author> </book>
[Definition: Boundary
whitespace is a sequence of consecutive whitespace characters
within the content of a direct element constructor, that is
delimited at each end either by the start or end of the content, or
by a DirectConstructor, or by an
EnclosedExpr. For this
purpose, characters generated by character references such as
 
or by CDataSections are not considered
to be whitespace characters.]
The boundary-space policy in the
static
context controls whether boundary whitespace is preserved by
element constructors. If boundary-space policy is
strip
, boundary whitespace is not considered
significant and is discarded. On the other hand, if boundary-space
policy is preserve
, boundary whitespace is considered
significant and is preserved.
Example:
<cat> <breed>{$b}</breed> <color>{$c}</color> </cat>
The constructed cat
element node has two child
element nodes named breed
and color
.
Whitespace surrounding the child elements will be stripped away by
the element constructor if boundary-space policy is
strip
.
Example:
<a> {"abc"} </a>
If boundary-space policy is strip
, this example is
equivalent to <a>abc</a>
. However, if
boundary-space policy is preserve
, this example is
equivalent to
<a> abc </a>
.
Example:
<a> z {"abc"}</a>
Since the whitespace surrounding the z
is not
boundary whitespace, it is always preserved. This example is
equivalent to <a> z abc</a>
.
Example:
<a> {"abc"}</a>
This example is equivalent to
<a> abc</a>
, regardless of the
boundary-space policy, because the space generated by the character
reference is not treated as a whitespace character.
Example:
<a>{" "}</a>
This example constructs an element containing two space characters, regardless of the boundary-space policy, because whitespace inside an enclosed expression is never considered to be boundary whitespace.
Note:
Element constructors treat attributes named
xml:space
as ordinary attributes. An
xml:space
attribute does not affect the handling of
whitespace by an element constructor.
XQuery allows an expression to generate a processing instruction node or a comment node. This can be accomplished by using a direct processing instruction constructor or a direct comment constructor. In each case, the syntax of the constructor expression is based on the syntax of a similar construct in XML.
[144] | DirPIConstructor |
::= | "<?" PITarget
(S DirPIContents)?
"?>" |
[145] | DirPIContents |
::= | (Char* - (Char* '?>'
Char*)) |
[142] | DirCommentConstructor |
::= | "<!--" DirCommentContents
"-->" |
[143] | DirCommentContents |
::= | ((Char - '-') | ('-'
(Char - '-')))* |
A direct processing instruction constructor creates a processing
instruction node whose target
property is PITarget and whose
content
property is DirPIContents. The
base-uri
property of the node is empty. The
parent
property of the node is empty.
The PITarget of a
processing instruction must not consist of the characters "XML" in
any combination of upper and lower case. The DirPIContents of a processing
instruction must not contain the string "?>
".
The following example illustrates a direct processing instruction constructor:
<?format role="output" ?>
A direct comment constructor creates a comment node whose
content
property is DirCommentContents. Its
parent
property is empty.
The DirCommentContents of a comment must not contain two consecutive hyphens or end with a hyphen. These rules are syntactically enforced by the grammar shown above.
The following example illustrates a direct comment constructor:
<!-- Tags are ignored in the following section -->
[148] | ComputedConstructor |
::= | CompDocConstructor |
An alternative way to create nodes is by using a computed
constructor. A computed constructor begins with a keyword that
identifies the type of node to be created: element
,
attribute
, document
, text
,
processing-instruction
, comment
, or
namespace
.
For those kinds of nodes that have names (element, attribute, and processing instruction nodes), the keyword that specifies the node kind is followed by the name of the node to be created. This name may be specified either as an EQName or as an expression enclosed in braces. [Definition: When an expression is used to specify the name of a constructed node, that expression is called the name expression of the constructor.]
[Definition: The final part of a computed constructor is an expression enclosed in braces, called the content expression of the constructor, that generates the content of the node.]
The following example illustrates the use of computed element and attribute constructors in a simple case where the names of the constructed nodes are constants. This example generates exactly the same result as the first example in 3.8.1 Direct Element Constructors:
element book { attribute isbn {"isbn-0060229357" }, element title { "Harold and the Purple Crayon"}, element author { element first { "Crockett" }, element last {"Johnson" } } }
[150] | CompElemConstructor |
::= | "element" (EQName |
("{" Expr "}")) "{" ContentExpr? "}" |
[192] | EQName |
::= | QName | URIQualifiedName |
[151] | ContentExpr |
::= | Expr |
[Definition: A computed element constructor creates an element node, allowing both the name and the content of the node to be computed.]
If the keyword element
is followed by an EQName, it
is expanded to an expanded QName as follows: if the EQName
has a URILiteral it is expanded using the specified URI; if the
EQName is a lexical
QName with a namespace prefix it is expanded using the
statically known namespaces; if the
EQName is a lexical
QName without a prefix it is implicitly qualified by the
default element/type namespace. The
resulting expanded QName is used as the
node-name
property of the constructed element node. If
expansion of the QName is not successful, a static error is raised [err:XPST0081].
If the keyword element
is followed by a name expression,
the name expression is processed as follows:
Atomization is
applied to the value of the name expression. If the result of
atomization is not a single atomic value of type
xs:QName
, xs:string
, or
xs:untypedAtomic
, a type error is raised [err:XPTY0004].
If the atomized value of the name expression is of type
xs:QName
, that expanded QName is used as the
node-name
property of the constructed element,
retaining the prefix part of the QName.
If the atomized value of the name expression is of type
xs:string
or xs:untypedAtomic
, that value
is converted to an expanded QName. If the string value
contains a namespace prefix, that prefix is resolved to a namespace URI
using the statically known namespaces. If the
string value contains no namespace prefix, it is treated as a local
name in the default element/type namespace. The
resulting expanded QName is used as the
node-name
property of the constructed element,
retaining the prefix part of the QName. If conversion of the
atomized name
expression to an expanded QName is not successful, a
dynamic error
is raised [err:XQDY0074].
A dynamic error is raised [err:XQDY0096] if the node-name of the constructed element node has any of the following properties:
Its namespace prefix is xmlns
.
Its namespace URI is
http://www.w3.org/2000/xmlns/
.
Its namespace prefix is xml
and its namespace URI
is not http://www.w3.org/XML/1998/namespace
.
Its namespace prefix is other than xml
and its
namespace URI is
http://www.w3.org/XML/1998/namespace
.
The content expression of a computed element constructor (if present) is processed in exactly the same way as an enclosed expression in the content of a direct element constructor, as described in Step 1e of 3.8.1.3 Content. The result of processing the content expression is a sequence of nodes called the content sequence. If the content expression is absent, the content sequence is an empty sequence.
Processing of the computed element constructor proceeds as follows:
If the content sequence contains a document node, the document node is replaced in the content sequence by its children.
Adjacent text nodes in the content sequence are merged into a single text node by concatenating their contents, with no intervening blanks. After concatenation, any text node whose content is a zero-length string is deleted from the content sequence.
If the content sequence contains an attribute node or a namespace node following a node that is not an attribute node or a namespace node, a type error is raised [err:XQTY0024].
The properties of the newly constructed element node are determined as follows:
node-name
is the expanded QName resulting from processing
the specified lexical
QName or name expression, as described above.
parent
is empty.
attributes
consist of all the attribute nodes in
the content sequence, in implementation-dependent order.
Note that the parent
property of each of these
attribute nodes has been set to the newly constructed element node.
If two or more attributes have the same node-name
, a
dynamic error
is raised [err:XQDY0025]. If an attribute named
xml:space
has a value other than preserve
or default
, a dynamic error may be raised [err:XQDY0092].
children
consist of all the element, text, comment,
and processing instruction nodes in the content sequence. Note that
the parent
property of each of these nodes has been
set to the newly constructed element node.
base-uri
is set to the following value:
If the constructed node has an attribute named
xml:base
, then the value of this attribute, resolved (if it is
relative) against the Dynamic Base URI.
Otherwise, the Dynamic Base URI.
in-scope-namespaces
are computed as described in
3.8.4 In-scope Namespaces of
a Constructed Element.
The nilled
property is false
.
The string-value
property is equal to the
concatenated contents of the text-node descendants in document
order.
The typed-value
property is equal to the
string-value
property, as an instance of
xs:untypedAtomic
.
If construction mode in the static context is
strip
, the type-name
property is
xs:untyped
. On the other hand, if construction mode is
preserve
, the type-name
property is
xs:anyType
.
The is-id
and is-idrefs
properties are
set to false
.
A computed element constructor might be used to make a modified
copy of an existing element. For example, if the variable
$e
is bound to an element with numeric content, the following constructor
might be used to create a new element with the same name and
attributes as $e
and with numeric content equal to
twice the value of $e
:
element {fn:node-name($e)} {$e/@*, 2 * fn:data($e)}
In this example, if $e
is bound by the expression
let $e := <length
units="inches">{5}</length>
, then the result of the
example expression is the element <length
units="inches">10</length>
.
Note:
The static
type of the expression fn:node-name($e)
is
xs:QName?
, denoting zero or one QName. Therefore, if
the Static Typing Feature is in effect,
the above example raises a static type error, since the name
expression in a computed element constructor is required to return
exactly one string or QName. In order to avoid the static type
error, the name expression fn:node-name($e)
could be
rewritten as fn:exactly-one(fn:node-name($e))
. If the
Static Typing Feature is not in
effect, the example can be successfully evaluated as written,
provided that $e
is bound to exactly one element node
with numeric content.
One important purpose of computed constructors is to allow the
name of a node to be computed. We will illustrate this feature by
an expression that translates the name of an element from one
language to another. Suppose that the variable $dict
is bound to a dictionary
element containing a sequence
of entry
elements, each of which encodes translations
for a specific word. Here is an example entry that encodes the
German and Italian variants of the word "address":
<entry word="address"> <variant xml:lang="de">Adresse</variant> <variant xml:lang="it">indirizzo</variant> </entry>
Suppose further that the variable $e
is bound to
the following element:
<address>123 Roosevelt Ave. Flushing, NY 11368</address>
Then the following expression generates a new element in which
the name of $e
has been translated into Italian and
the content of $e
(including its attributes, if any)
has been preserved. The first enclosed expression after the
element
keyword generates the name of the element, and
the second enclosed expression generates the content and
attributes:
element {$dict/entry[@word=name($e)]/variant[@xml:lang="it"]} {$e/@*, $e/node()}
The result of this expression is as follows:
<indirizzo>123 Roosevelt Ave. Flushing, NY 11368</indirizzo>
Note:
As in the previous example, if the Static
Typing Feature is in effect, the enclosed expression that
computes the element name in the above computed element constructor
must be wrapped in a call to the fn:exactly-one
function in order to avoid a static type error.
Additional examples of computed element constructors can be found in I.3 Recursive Transformations.
[152] | CompAttrConstructor |
::= | "attribute" (EQName |
("{" Expr "}")) "{" Expr? "}" |
[192] | EQName |
::= | QName | URIQualifiedName |
A computed attribute constructor creates a new attribute node, with its own node identity.
If the keyword attribute
is followed by an EQName,
it is expanded to an expanded QName as follows: if the EQName
has a URILiteral it is expanded using the specified URI; if the
EQName is a lexical
QName with a namespace prefix it is expanded using the
statically known namespaces; if the
EQName is a lexical
QName without a prefix, the expanded QName is in no namespace.
The resulting expanded QName (including its prefix) is
used as the node-name
property of the constructed
attribute node. If expansion of the QName is not successful, a
static error is
raised [err:XPST0081].
If the keyword attribute
is followed by a name expression,
the name expression is processed as follows:
Atomization is
applied to the result of the name expression. If the result of
atomization is
not a single atomic value of type xs:QName
,
xs:string
, or xs:untypedAtomic
, a
type error is
raised [err:XPTY0004].
If the atomized value of the name expression is of type
xs:QName
:
If the expanded QName returned by the atomized name expression has a namespace URI but has no prefix, it is given an implementation-dependent prefix.
Note:
This step is necessary because attributes have no default namespace. Therefore any attribute name that has a namespace URI must also have a prefix.
The resulting expanded QName (including its prefix) is
used as the node-name
property of the constructed
attribute node.
If the atomized value of the name expression is of type
xs:string
or xs:untypedAtomic
, that value
is converted to an expanded QName. If the string value
contains a namespace prefix, that prefix is resolved to a namespace
URI using the statically known namespaces. If the
string value contains no namespace prefix, it is treated as a local
name in no namespace. The resulting expanded QName (including its prefix) is
used as the node-name
property of the constructed
attribute. If conversion of the atomized name expression to an expanded QName is
not successful, a dynamic error is raised [err:XQDY0074].
A dynamic error is raised [err:XQDY0044] if the node-name of the constructed attribute node has any of the following properties:
Its namespace prefix is xmlns
.
It has no namespace prefix and its local name is
xmlns
.
Its namespace URI is
http://www.w3.org/2000/xmlns/
.
Its namespace prefix is xml
and its namespace URI
is not http://www.w3.org/XML/1998/namespace
.
Its namespace prefix is other than xml
and its
namespace URI is
http://www.w3.org/XML/1998/namespace
.
The content expression of a computed attribute constructor is processed as follows:
Atomization is applied to the result of the content expression, converting it to a sequence of atomic values. (If the content expression is absent, the result of this step is an empty sequence.)
If the result of atomization is an empty sequence, the value of the attribute is the zero-length string. Otherwise, each atomic value in the atomized sequence is cast into a string.
The individual strings resulting from the previous step are
merged into a single string by concatenating them with a single
space character between each pair. The resulting string becomes the
string-value
property of the new attribute node. The
type
annotation (type-name
property) of the new
attribute node is xs:untypedAtomic
. The
typed-value
property of the attribute node is the same
as its string-value
, as an instance of
xs:untypedAtomic
.
The parent
property of the attribute node is set to
empty.
If the attribute name is xml:id
, then
xml:id
processing is performed as defined in [XML ID]. This ensures that the attribute node has the
type xs:ID
and that its value is properly normalized.
If an error is encountered during xml:id
processing,
an implementation may raise a dynamic error [err:XQDY0091].
If the attribute name is xml:id
, the
is-id
property of the resulting attribute node is set
to true
; otherwise the is-id
property is
set to false
. The is-idrefs
property of
the attribute node is unconditionally set to
false
.
If the attribute name is xml:space
and the
attribute value is other than preserve
or
default
, a dynamic error MAY be raised [err:XQDY0092].
Example:
attribute size {4 + 3}
The string
value of the size
attribute is "7
"
and its type is xs:untypedAtomic
.
Example:
attribute { if ($sex = "M") then "husband" else "wife" } { <a>Hello</a>, 1 to 3, <b>Goodbye</b> }
The name of the constructed attribute is either
husband
or wife
. Its string value is
"Hello 1 2 3 Goodbye
".
[149] | CompDocConstructor |
::= | "document" "{" Expr
"}" |
All document node constructors are computed constructors. The result of a document node constructor is a new document node, with its own node identity.
A document node constructor is useful when the result of a query
is to be a document in its own right. The following example
illustrates a query that returns an XML document containing a root
element named author-list
:
document { <author-list> {fn:doc("bib.xml")/bib/book/author} </author-list> }
The content expression of a document node constructor is processed in exactly the same way as an enclosed expression in the content of a direct element constructor, as described in Step 1e of 3.8.1.3 Content. The result of processing the content expression is a sequence of nodes called the content sequence. Processing of the document node constructor then proceeds as follows:
If the content sequence contains a document node, the document node is replaced in the content sequence by its children.
Adjacent text nodes in the content sequence are merged into a single text node by concatenating their contents, with no intervening blanks. After concatenation, any text node whose content is a zero-length string is deleted from the content sequence.
If the content sequence contains an attribute node, a type error is raised [err:XPTY0004].
If the content sequence contains a namespace node, a type error is raised [err:XPTY0004].
The properties of the newly constructed document node are determined as follows:
base-uri
is set to the Dynamic Base
URI.
children
consist of all the element, text, comment,
and processing instruction nodes in the content sequence. Note that
the parent
property of each of these nodes has been
set to the newly constructed document node.
The unparsed-entities
and document-uri
properties are empty.
The string-value
property is equal to the
concatenated contents of the text-node descendants in document
order.
The typed-value
property is equal to the
string-value
property, as an instance of
xs:untypedAtomic
.
No validation is performed on the constructed document node. The [XML 1.0] rules that govern the structure of an XML document (for example, the document node must have exactly one child that is an element node) are not enforced by the XQuery document node constructor.
[157] | CompTextConstructor |
::= | "text" "{" Expr
"}" |
All text node constructors are computed constructors. The result of a text node constructor is a new text node, with its own node identity.
The content expression of a text node constructor is processed as follows:
Atomization is applied to the value of the content expression, converting it to a sequence of atomic values.
If the result of atomization is an empty sequence, no text node is constructed. Otherwise, each atomic value in the atomized sequence is cast into a string.
The individual strings resulting from the previous step are
merged into a single string by concatenating them with a single
space character between each pair. The resulting string becomes the
content
property of the constructed text node.
The parent
property of the constructed text node is
set to empty.
Note:
It is possible for a text node constructor to construct a text node containing a zero-length string. However, if used in the content of a constructed element or document node, such a text node will be deleted or merged with another text node.
The following example illustrates a text node constructor:
text {"Hello"}
[159] | CompPIConstructor |
::= | "processing-instruction" (NCName | ("{" Expr "}")) "{" Expr? "}" |
A computed processing instruction constructor (CompPIConstructor) constructs a new processing instruction node with its own node identity.
If the keyword processing-instruction
is followed
by an NCName, that NCName is used as the target
property of the constructed node. If the keyword
processing-instruction
is followed by a name expression,
the name expression is processed as follows:
Atomization is
applied to the value of the name expression. If the result of
atomization is
not a single atomic value of type xs:NCName
,
xs:string
, or xs:untypedAtomic
, a
type error is
raised [err:XPTY0004].
If the atomized value of the name expression is of type
xs:string
or xs:untypedAtomic
, that value
is cast to the type xs:NCName
. If the value cannot be
cast to xs:NCName
, a dynamic error is raised [err:XQDY0041].
The resulting NCName is then used as the target
property of the newly constructed processing instruction node.
However, a dynamic error is raised if the NCName is
equal to "XML
" (in any combination of upper and lower
case) [err:XQDY0064].
The content expression of a computed processing instruction constructor is processed as follows:
Atomization is applied to the value of the content expression, converting it to a sequence of atomic values. (If the content expression is absent, the result of this step is an empty sequence.)
If the result of atomization is an empty sequence, it is
replaced by a zero-length string. Otherwise, each atomic value in
the atomized sequence is cast into a string. If any of the
resulting strings contains the string "?>
", a
dynamic error
[err:XQDY0026] is
raised.
The individual strings resulting from the previous step are
merged into a single string by concatenating them with a single
space character between each pair. Leading whitespace is removed
from the resulting string. The resulting string then becomes the
content
property of the constructed processing
instruction node.
The remaining properties of the new processing instruction node are determined as follows:
The parent
property is empty.
The base-uri
property is empty.
The following example illustrates a computed processing instruction constructor:
let $target := "audio-output", $content := "beep" return processing-instruction {$target} {$content}
The processing instruction node constructed by this example might be serialized as follows:
<?audio-output beep?>
[158] | CompCommentConstructor |
::= | "comment" "{" Expr
"}" |
A computed comment constructor (CompCommentConstructor) constructs a new comment node with its own node identity. The content expression of a computed comment constructor is processed as follows:
Atomization is applied to the value of the content expression, converting it to a sequence of atomic values.
If the result of atomization is an empty sequence, it is replaced by a zero-length string. Otherwise, each atomic value in the atomized sequence is cast into a string.
The individual strings resulting from the previous step are
merged into a single string by concatenating them with a single
space character between each pair. The resulting string becomes the
content
property of the constructed comment node.
It is a dynamic error [err:XQDY0072] if the result of the content expression of a computed comment constructor contains two adjacent hyphens or ends with a hyphen.
The parent
property of the constructed comment node
is set to empty.
The following example illustrates a computed comment constructor:
let $homebase := "Houston" return comment {fn:concat($homebase, ", we have a problem.")}
The comment node constructed by this example might be serialized as follows:
<!--Houston, we have a problem.-->
[153] | CompNamespaceConstructor |
::= | "namespace" (Prefix |
("{" PrefixExpr "}")) "{"
URIExpr? "}" |
[155] | PrefixExpr |
::= | Expr |
[156] | URIExpr |
::= | Expr |
A computed namespace constructor creates a new namespace node, with its own node identity. The parent of the newly created namespace node is empty.
If the constructor specifies a Prefix
, it is used
as the prefix for the namespace node.
If the constructor specifies a PrefixExpr
, the
prefix expression is evaluated as follows:
Atomization is
applied to the result of the PrefixExpr
.
If the result of atomization is a single atomic value of type
xs:NCName
, xs:string
, or
xs:untypedAtomic
, it is used as the
prefix
property of the newly constructed namespace
node; if it can not be cast to xs:NCName
, dynamic error is
raised [err:XQDY0074]. If the result is the empty
sequence or an empty string, the prefix
property of
the newly constructed namespace node is empty. For any other
result, a type
error is raised [err:XPTY0004].
The URIExpr
is evaluated, and the result is cast to
xs:anyURI
to create the URI
property for
the newly created node.
An error [err:XQDY0101] is raised if a computed namespace constructor attempts to do any of the following:
Bind the prefix xml
to some namespace URI other
than http://www.w3.org/XML/1998/namespace
.
Bind a prefix other than xml
to the namespace URI
http://www.w3.org/XML/1998/namespace
.
Bind the prefix xmlns
to any namespace URI.
Bind a prefix to the namespace URI
http://www.w3.org/2000/xmlns/
.
By itself, a computed namespace constructor has no effect on in-scope namespaces, but if an element constructor's content sequence contains a namespace node, the namespace binding it represents is added to the elements in-scope namespaces.
A computed namespace constructor has no effect on the statically known namespaces.
Note:
The newly created namespace node has all properties defined for a namespace node in the data model. Like all nodes, it has identity. Like all nodes which do not share a common parent, the relative order of these nodes is implementation dependent. As defined in the data model, the name of the node is the prefix, and the string value of the node is the URI.
Examples:
A computed namespace constructor with a prefix:
namespace a {"http://a.example.com" }
A computed namespace constructor with a prefix expression:
namespace {"a"} {"http://a.example.com" }
A computed namespace constructor with an empty prefix:
namespace { "" } {"http://a.example.com" }
Computed namespace constructors are generally used to add to the in-scope namespaces of elements created with element constructors:
<age xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> { namespace xs {"http://www.w3.org/2001/XMLSchema"}, attribute xsi:type {"xs:integer"}, 23 }</age>
In the above example, note that the xsi
namespace
binding is created for the element because it is used in an
attribute name. The attribute's content is simply character data,
and has no effect on namespace bindings. The computed namespace
constructor ensures that the xs
binding is
created.
Computed namespace constructors have no effect on the statically known namespaces. If the prefix a is not already defined in the statically known namespaces, the following expression results in a static error [err:XPST0081].
<a:form> { namespace a { "http://a.example.com" } } </a:form>
An element node constructed by a direct or computed element
constructor has an in-scope namespaces property that
consists of a set of namespace bindings. The in-scope
namespaces of an element node may affect the way the node is
serialized (see 2.2.4
Serialization), and may also affect the behavior of certain
functions that operate on nodes, such as fn:name
. Note
the difference between in-scope namespaces, which is a
dynamic property of an element node, and statically known namespaces, which is a
static property of an expression. Also note that one of the
namespace bindings in the in-scope namespaces may have no prefix
(denoting the default namespace for the given element). The
in-scope namespaces of a constructed element node consist of the
following namespace bindings:
A namespace binding is created for each namespace declared in the current element constructor by a namespace declaration attribute.
A namespace binding is created for each namespace node in the context sequence of the current element constructor.
A namespace binding is created for each namespace that is declared in a namespace declaration attribute of an enclosing direct element constructor and not overridden by the current element constructor or an intermediate constructor.
A namespace binding is always created to bind the prefix
xml
to the namespace URI
http://www.w3.org/XML/1998/namespace
.
For each prefix used in the name of the constructed element or in the names of its attributes, a namespace binding must exist. If a namespace binding does not already exist for one of these prefixes, a new namespace binding is created for it. If this would result in a conflict, because it would require two different bindings of the same prefix, then the prefix used in the node name is changed to an arbitrary implementation-dependent prefix that does not cause such a conflict, and a namespace binding is created for this new prefix. If there is an in-scope default namespace, then a binding is created between the empty prefix and that URI.
Note:
Copy-namespaces mode does not affect the namespace bindings of a newly constructed element node. It applies only to existing nodes that are copied by a constructor expression.
In an element constructor, if two or more namespace bindings in the in-scope bindings would have the same prefix, then an error is raised if they have different URIs [err:XQTY0102]; if they would have the same prefix and URI, duplicate bindings are ignored.
The following query serves as an example:
declare namespace p="http://example.com/ns/p"; declare namespace q="http://example.com/ns/q"; declare namespace f="http://example.com/ns/f"; <p:a q:b="{f:func(2)}" xmlns:r="http://example.com/ns/r"/>
The in-scope namespaces of the resulting
p:a
element consists of the following namespace
bindings:
p = "http://example.com/ns/p"
q = "http://example.com/ns/q"
r = "http://example.com/ns/r"
xml = "http://www.w3.org/XML/1998/namespace"
The namespace bindings for p
and q
are
added to the result element because their respective namespaces are
used in the names of the element and its attributes. The namespace
binding r="http://example.com/ns/r"
is added to the
in-scope namespaces of the constructed element because it is
defined by a namespace declaration attribute, even
though it is not used in a name.
No namespace binding corresponding to
f="http://example.com/ns/f"
is created, because the
namespace prefix f
appears only in the query prolog
and is not used in an element or attribute name of the constructed
node. This namespace binding does not appear in the query result,
even though it is present in the statically known namespaces and is
available for use during processing of the query.
Note that the following constructed element, if nested within a
validate
expression, cannot be validated:
<p xsi:type="xs:integer">3</p>
The constructed element will have namespace bindings for the
prefixes xsi
(because it is used in a name) and
xml
(because it is defined for every constructed
element node). During validation of the constructed element, the
validator will be unable to interpret the namespace prefix
xs
because it is has no namespace binding. Validation
of this constructed element could be made possible by providing a
namespace declaration attribute, as
in the following example:
<p xmlns:xs="http://www.w3.org/2001/XMLSchema" xsi:type="xs:integer">3</p>
XQuery provides a versatile expression called a FLWOR expression
that may contain multiple clauses. The FLWOR expression can be used
for many purposes, including iterating over sequences, joining
multiple documents, and performing grouping and aggregation. The
name FLWOR, pronounced "flower", is suggested by the keywords
for
, let
, where
, order
by
, and return
, which introduce some of the
clauses used in FLWOR expressions (but this is not a complete list
of such clauses.)
The complete syntax of a FLWOR expression is shown here, and relevant parts of the syntax are repeated in subsequent sections of this document.
The semantics of FLWOR expressions are based on a concept called
a tuple stream. [Definition: A
tuple stream is an ordered sequence of zero or more
tuples.] [Definition: A tuple is a set of zero or
more named variables, each of which is bound to a value that is an
XDM
instance.] Each tuple stream is homogeneous in the sense that
all its tuples contain variables with the same names and the same
static types. The
following example illustrates a tuple stream consisting of four
tuples, each containing three variables named $x
,
$y
, and $z
:
($x = 1003, $y = "Fred", $z = <age>21</age>) ($x = 1017, $y = "Mary", $z = <age>35</age>) ($x = 1020, $y = "Bill", $z = <age>18</age>) ($x = 1024, $y = "John", $z = <age>29</age>)
Note:
In this section, tuple streams are represented as shown in the above example. Each tuple is on a separate line and is enclosed in parentheses, and the variable bindings inside each tuple are separated by commas. This notation does not represent XQuery syntax, but is simply a representation of a tuple stream for the purpose of defining the semantics of FLWOR expressions.
Tuples and tuple streams are not part of the data model. They exist only as conceptual intermediate results during the processing of a FLWOR expression.
A FLWOR expression consists of an initial clause, zero or more intermediate clauses, and a final clause. Conceptually, the initial clause generates a tuple stream. Each intermediate clause takes the tuple stream generated by the previous clause as input and generates a (possibly different) tuple stream as output. The final clause takes a tuple stream as input and, for each tuple in this tuple stream, generates an XDM instance; the final result of the FLWOR expression is the ordered concatenation of these XDM instances.
The initial clause in a FLWOR expression may be a
for
, let
, window
, or
count
clause. Intermediate clauses may be
for
, let
, window
,
count
, where
, group by
, or
order by
clauses. These intermediate clauses may be
repeated as many times as desired, in any order. The final clause
of the FLWOR expression must be a return
clause. The
semantics of the various clauses are described in the following
sections.
The following clauses in FLWOR expressions bind values to
variables: for
, let
, window
,
and count
(in addition, a group by
clause
changes the values of variables that were previously bound.) In
each case, binding of variables is governed by the following
rules:
The scope of a bound variable includes all subexpressions of the
containing FLWOR that appear after the variable binding. The scope
does not include the expression to which the variable is bound. The
following code fragment, containing two let
clauses,
illustrates how variable bindings may reference variables that were
bound in earlier clauses, or in earlier bindings in the same
clause:
let $x := 47, $y := f($x) let $z := g($x, $y)
A given variable may be bound more than once in a FLWOR expression, or even within one clause of a FLWOR expression. In such a case, each new binding occludes the previous one, which becomes inaccessible in the remainder of the FLWOR expression.
[Definition: A variable binding may be
accompanied by a type declaration, which consists of the
keyword as
followed by the static type of the
variable, declared using the syntax in 2.5.4 SequenceType Syntax.] At
run time, if the value bound to the variable does not match the
declared type according to the rules for SequenceType matching, a type error is raised
[err:XPTY0004]. For
example, the following let
clause raises a type error because the
variable $salary
has a type declaration that is not
satisfied by the value that is bound to it:
let $salary as xs:decimal := "cat"
[Definition: In a for
clause or
window
clause, when an expression is preceded by the
keyword in
, the value of that expression is called a
binding sequence.] The for
and
window
clauses iterate over their binding sequences,
producing multiple bindings for one or more variables. Details on
how binding sequences are used in for
and
window
clauses are described in the following
sections.
[44] | ForClause |
::= | "for" ForBinding
("," ForBinding)* |
[45] | ForBinding |
::= | "$" VarName TypeDeclaration? AllowingEmpty? PositionalVar? "in" ExprSingle |
[164] | TypeDeclaration |
::= | "as" SequenceType |
[46] | AllowingEmpty |
::= | "allowing" "empty" |
[47] | PositionalVar |
::= | "at" "$" VarName |
A for
clause is used for iteration. Each variable
in a for
clause iterates over a sequence and is bound
in turn to each item in the sequence.
If a for
clause contains multiple variables, it is
semantically equivalent to multiple for
clauses, each
containing one of the variables in the original for
clause.
Example:
The clause
for $x in $expr1, $y in $expr2
is semantically equivalent to:
for $x in $expr1 for $y in $expr2
In the remainder of this section, we define the semantics of a
for
clause containing a single variable and an
associated expression (following the keyword in
) whose
value is called the binding sequence for that variable.
If a single-variable for
clause is the initial
clause in a FLWOR expression, it iterates over its binding
sequence, binding the variable to each item in turn. The
resulting sequence of variable bindings becomes the initial tuple
stream that serves as input to the next clause of the FLWOR
expression. If ordering mode is ordered
, the
order of tuples in the tuple stream preserves the order of the
binding
sequence; otherwise the order of the tuple stream is implementation-dependent.
If the binding sequence contains no items, the
output tuple stream depends on whether allowing empty
is specified. If allowing empty
is specified, the
output tuple stream consists of one tuple in which the variable is
bound to an empty sequence. If allowing empty
is not
specified, the output tuple stream consists of zero tuples.
The following examples illustrates tuple streams that are
generated by initial for
clauses:
Initial clause:
for $x in (100, 200, 300)
or (equivalently):
for $x allowing empty in (100, 200, 300)
Output tuple stream:
($x = 100) ($x = 200) ($x = 300)
Initial clause:
for $x in ()
Output tuple stream contains no tuples.
Initial clause:
for $x allowing empty in ()
Output tuple stream:
($x = ())
[Definition: A positional
variable is a variable that is preceded by the keyword
at
.] A positional variable may be associated with a
variable that is bound in a for
clause. In this case,
as the main variable iterates over the items in its binding
sequence, the positional variable iterates over the integers
that represent the ordinal numbers of these items in the binding
sequence, starting with one. Each tuple in the output tuple
stream contains bindings for both the main variable and the
positional variable. If the binding sequence is empty and
allowing empty
is specified, the positional variable
in the output tuple is bound to the integer zero. Positional
variables always have the implied type xs:integer
. The
expanded
QName of a positional variable must be distinct from the
expanded
QName of the main variable with which it is associated
[err:XQST0089].
The following examples illustrate how a positional variable would have affected the results of the previous examples that generated tuples:
Initial clause:
for $x at $i in (100, 200, 300)
Output tuple stream:
($x = 100, $i = 1) ($x = 200, $i = 2) ($x = 300, $i = 3)
Initial clause:
for $x allowing empty at $i in ()
Output tuple stream:
($x = (), $i = 0)
If a single-variable for
clause is an intermediate
clause in a FLWOR expression, its binding sequence is evaluated for each
input tuple, given the bindings in that input tuple. Each input
tuple generates zero or more tuples in the output tuple stream.
Each of these output tuples consists of the original variable
bindings of the input tuple plus a binding of the new variable to
one of the items in its binding sequence.
Note:
Although the binding sequence is conceptually evaluated independently for each input tuple, an optimized implementation may sometimes be able to avoid re-evaluating the binding sequence if it can show that the variables that the binding sequence depends on have the same values as in a previous evaluation.
For a given input tuple, if the binding sequence for the new
variable in the for
clause contains no items, the
result depends on whether allowing empty
is specified.
If allowing empty
is specified, the input tuple
generates one output tuple, with the original variable bindings
plus a binding of the new variable to an empty sequence. If
allowing empty
is not specified, the input tuple
generates zero output tuples (it is not represented in the output
tuple stream.)
If the new variable introduced by a for
clause has
an associated positional variable, the output
tuples generated by the for
clause also contain
bindings for the positional variable. In this case, as
the new variable is bound to each item in its binding
sequence, the positional variable is bound to the
ordinal position of that item within the binding
sequence, starting with one. Note that, since the positional
variable represents a position within a binding
sequence, the output tuples corresponding to each input tuple
are independently numbered, starting with one. For a given input
tuple, if the binding sequence is empty and
allowing empty
is specified, the positional
variable in the output tuple is bound to the integer zero.
If ordering
mode is ordered
, the tuples in the output tuple
stream are ordered primarily by the order of the input tuples from
which they are derived, and secondarily by the order of the
binding
sequence for the new variable; otherwise the order of the
output tuple stream is implementation-dependent.
The following examples illustrates the effects of intermediate
for
clauses:
Input tuple stream:
($x = 1) ($x = 2) ($x = 3) ($x = 4)
Intermediate for
clause:
for $y in ($x to 3)
Output tuple stream (assuming ordering mode is ordered
):
($x = 1, $y = 1) ($x = 1, $y = 2) ($x = 1, $y = 3) ($x = 2, $y = 2) ($x = 2, $y = 3) ($x = 3, $y = 3)
Note:
In this example, there is no output tuple that corresponds to
the input tuple ($x = 4)
because, when the
for
clause is evaluated with the bindings in this
input tuple, the resulting binding sequence for $y
is
empty.
This example shows how the previous example would have been affected by a positional variable (assuming the same input tuple stream):
for $y at $j in ($x to 3)
Output tuple stream (assuming ordering mode is ordered
):
($x = 1, $y = 1, $j = 1) ($x = 1, $y = 2, $j = 2) ($x = 1, $y = 3, $j = 3) ($x = 2, $y = 2, $j = 1) ($x = 2, $y = 3, $j = 2) ($x = 3, $y = 3, $j = 1)
This example shows how the previous example would have been
affected by allowing empty
. Note that allowing
empty
causes the input tuple ($x = 4)
to be
represented in the output tuple stream, even though the binding sequence
for $y
contains no items for this input tuple. This
example illustrates that allowing empty
in a
for
clause serves a purpose similar to that of an
"outer join" in a relational database query. (Assume the same input
tuple stream as in the previous example.)
for $y allowing empty at $j in ($x to 3)
Output tuple stream (assuming ordering mode is ordered
):
($x = 1, $y = 1, $j = 1) ($x = 1, $y = 2, $j = 2) ($x = 1, $y = 3, $j = 3) ($x = 2, $y = 2, $j = 1) ($x = 2, $y = 3, $j = 2) ($x = 3, $y = 3, $j = 1) ($x = 4, $y = (), $j = 0)
This example shows how a for
clause that binds two
variables is semantically equivalent to two for
clauses that bind one variable each. We assume that this
for
clause occurs at the beginning of a FLWOR
expression. It is equivalent to an initial single-variable
for
clause that provides an input tuple stream to an
intermediate single-variable for
clause.
for $x in (1, 2, 3, 4), $y in ($x to 3)
Output tuple stream (assuming ordering mode is ordered
):
($x = 1, $y = 1) ($x = 1, $y = 2) ($x = 1, $y = 3) ($x = 2, $y = 2) ($x = 2, $y = 3) ($x = 3, $y = 3)
In the above examples, if ordering mode had been
unordered
, the output tuple streams would have
consisted of the same tuples, with the same values for the
positional variables, but the
ordering of the tuples would have been implementation-dependent.
A for
clause may contain one or more type
declarations, identified by the keyword as
. The
semantics of type declarations are defined in
3.9.1 Variable Bindings.
[48] | LetClause |
::= | "let" LetBinding
("," LetBinding)* |
[49] | LetBinding |
::= | "$" VarName TypeDeclaration? ":=" ExprSingle |
[164] | TypeDeclaration |
::= | "as" SequenceType |
The purpose of a let
clause is to bind values to
one or more variables. Each variable is bound to the result of
evaluating an expression.
If a let
clause contains multiple variables, it is
semantically equivalent to multiple let
clauses, each
containing a single variable. For example, the clause
let $x := $expr1, $y := $expr2
is semantically equivalent to the following sequence of clauses:
let $x := $expr1 let $y := $expr2
In the remainder of this section, we define the semantics of a
let
clause containing a single variable V and
an associated expression E.
If a single-variable let
clause is the initial
clause in a FLWOR expression, it simply binds the variable
V to the result of the expression E. The result
of the let
clause is a tuple stream consisting of one
tuple with a single binding that binds V to the result of
E. This tuple stream serves as input to the next clause in
the FLWOR expression.
If a single-variable let
clause is an intermediate
clause in a FLWOR expression, it adds a new binding for variable
V to each tuple in the input tuple stream. For each input
tuple, the value bound to V is the result of evaluating
expression E, given the bindings that are already present
in that input tuple. The resulting tuples become the output tuple
stream of the let
clause.
The number of tuples in the output tuple stream of an
intermediate let
clause is the same as the number of
tuples in the input tuple stream. The number of bindings in the
output tuples is one more than the number of bindings in the input
tuples, unless the input tuples already contain bindings for
V; in this case, the new binding for V occludes
(replaces) the earlier binding for V, and the number of
bindings is unchanged.
A let
clause may contain one or more type
declarations, identified by the keyword as
. The
semantics of type declarations are defined in 3.9.1 Variable Bindings.
The following code fragment illustrates how a for
clause and a let
clause can be used together. The
for
clause produces an initial tuple stream containing
a binding for variable $d
to each department number
found in a given input document. The let
clause adds
an additional binding to each tuple, binding variable
$e
to a sequence of employees whose department number
matches the value of $d
in that tuple.
for $d in fn:doc("depts.xml")/depts/deptno let $e := fn:doc("emps.xml")/emps/emp[deptno eq $d]
[50] | WindowClause |
::= | "for" (TumblingWindowClause |
SlidingWindowClause) |
[51] | TumblingWindowClause |
::= | "tumbling" "window" "$" VarName TypeDeclaration? "in" ExprSingle WindowStartCondition
WindowEndCondition? |
[52] | SlidingWindowClause |
::= | "sliding" "window" "$" VarName TypeDeclaration? "in" ExprSingle WindowStartCondition
WindowEndCondition |
[53] | WindowStartCondition |
::= | "start" WindowVars
"when" ExprSingle |
[54] | WindowEndCondition |
::= | "only"? "end" WindowVars "when" ExprSingle |
[55] | WindowVars |
::= | ("$" CurrentItem)? PositionalVar? ("previous" "$"
PreviousItem)? ("next" "$"
NextItem)? |
[56] | CurrentItem |
::= | EQName |
[47] | PositionalVar |
::= | "at" "$" VarName |
[57] | PreviousItem |
::= | EQName |
[58] | NextItem |
::= | EQName |
Like a for
clause, a window
clause
iterates over its binding sequence and generates a
sequence of tuples. In the case of a window
clause,
each tuple represents a window. [Definition: A window is a sequence of
consecutive items drawn from the binding sequence.] Each window is
represented by at least one and at most nine bound variables. The
variables have user-specified names, but their roles are as
follows:
Window-variable: Bound to the sequence of items from the binding sequence that comprise the window.
Start-item: (Optional) Bound to the first item in the window.
Start-item-position: (Optional) Bound to the ordinal
position of the first window item in the binding
sequence. Start-item-position is a positional
variable. Its type is xs:integer
, and its
expanded
QName must be distinct from the expanded QName of start-item
[err:XQST0089].
Start-previous-item: (Optional) Bound to the item in the binding sequence that precedes the first item in the window (empty sequence if none).
Start-next-item: (Optional) Bound to the item in the binding sequence that follows the first item in the window (empty sequence if none).
End-item: (Optional) Bound to the last item in the window.
End-item-position: (Optional) Bound to the ordinal
position of the last window item in the binding sequence.
End-item-position is a positional variable. Its type is
xs:integer
, and its expanded QName must be distinct from the
expanded
QName of end-item [err:XQST0089].
End-previous-item: (Optional) Bound to the item in the binding sequence that precedes the last item in the window (empty sequence if none).
End-next-item: (Optional) Bound to the item in the binding sequence that follows the last item in the window (empty sequence if none).
All variables in a window
clause must have distinct
names; otherwise a static error is raised [err:XQST0103].
The following is an example of a window
clause that
binds nine variables to the roles listed above. In this example,
the variables are named $w
, $s
,
$spos
, $sprev
, $snext
,
$e
, $epos
, $eprev
, and
$enext
respectively. A window
clause
always binds the window variable, but typically binds only a subset
of the other variables.
for tumbling window $w in (2, 4, 6, 8, 10) start $s at $spos previous $sprev next $snext when true() end $e at $epos previous $eprev next $enext when true()
Windows are created by iterating over the items in the binding
sequence, in order, identifying the start item and the end item
of each window by evaluating the WindowStartCondition and
the WindowEndCondition. Each of
these conditions is satisfied if the effective boolean
value of the expression following the when
keyword
is true
. The start item of the window is an item that
satisfies the WindowStartCondition (see
3.9.4.1 Tumbling Windows
and 3.9.4.2 Sliding
Windows for a more complete explanation.) The end item of
the window is the first item in the binding sequence, beginning with
the start item, that satisfies the WindowEndCondition (again,
see 3.9.4.1 Tumbling
Windows and 3.9.4.2
Sliding Windows for more details.) Each window contains its
start item, its end item, and all items that occur between them in
the binding
sequence. If the end item is the start item, then the window
contains only one item. If a start item is identified, but no
following item in the binding sequence satisfies the WindowEndCondition, then the
only
keyword determines whether a window is generated:
if only end
is specified, then no window is generated;
otherwise, the end item is set to the last item in the binding sequence
and a window is generated.
In the above example, the WindowStartCondition and
WindowEndCondition
are both true()
, which causes each tuple in the
binding
sequence to be in a separate window. Typically, the WindowStartCondition and
WindowEndCondition
are expressed in terms of bound variables. For example, the
following WindowStartCondition might
be used to start a new window for every item in the binding sequence
that is larger than both the previous item and the following
item:
start $s previous $sprev next $snext when $s > $sprev and $s > $snext
The scoping rules for the variables bound by a
window
clause are as follows:
In the when
-expression of the WindowStartCondition, the
following variables (identified here by their roles) are in scope
(if bound): start-item, start-item-position,
start-previous-item, start-next-item.
In the when
-expression of the WindowEndCondition, the
following variables (identified here by their roles) are in scope
(if bound): start-item, start-item-position,
start-previous-item, start-next-item, end-item, end-item-position,
end-previous-item, end-next-item.
In the clauses of the FLWOR expression that follow the
window
clause, all nine of the variables bound by the
window
clause (including window-variable) are
in scope (if bound).
In a window
clause, the keyword
tumbling
or sliding
determines the way in
which the starting item of each window is identified, as explained
in the following sections.
If the window type is tumbling
, then windows never
overlap. The search for the start of the first window begins at the
beginning of the binding sequence. After each window is
generated, the search for the start of the next window begins with
the item in the binding sequence that occurs after the
ending item of the last generated window. Thus, no item that occurs
in one window can occur in another window drawn from the same
binding
sequence. In a tumbling window clause, the end
clause is optional; if it is omitted, the start
clause
is applied to identify all potential starting items in the
binding
sequence, and a window is constructed for each starting item,
including all items from that starting item up to the item before
the next window's starting item, or the end of the binding
sequence, whichever comes first.
The following examples illustrate the use of tumbling windows.
Show non-overlapping windows of three items.
for tumbling window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when fn:true() only end at $e when $e - $s eq 2 return <window>{ $w }</window>
Result of the above query:
<window>2 4 6</window> <window>8 10 12</window>
Show averages of non-overlapping three-item windows.
for tumbling window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when fn:true() only end at $e when $e - $s eq 2 return avg($w)
Result of the above query:
4 10
Show first and last items in each window of three items.
for tumbling window $w in (2, 4, 6, 8, 10, 12, 14) start $first at $s when fn:true() only end $last at $e when $e - $s eq 2 return <window>{ $first, $last }</window>
Result of the above query:
<window>2 6</window> <window>8 12</window>
Show non-overlapping windows of up to three items (illustrates
end
clause without the only
keyword).
for tumbling window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when fn:true() end at $e when $e - $s eq 2 return <window>{ $w }</window>
Result of the above query:
<window>2 4 6</window> <window>8 10 12</window> <window>14</window>
Show non-overlapping windows of up to three items (illustrates
use of start
without explicit end
).
for tumbling window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when $s mod 3 = 1 return <window>{ $w }</window>
Result of the above query:
<window>2 4 6</window> <window>8 10 12</window> <window>14</window>
Show non-overlapping sequences starting with a number divisible by 3.
for tumbling window $w in (2, 4, 6, 8, 10, 12, 14) start $first when $first mod 3 = 0 return <window>{ $w }</window>
Result of the above query:
<window>6 8 10</window> <window>12 14</window>
If the window type is sliding window
, then windows
may overlap. Every item in the binding sequence that satisfies the
WindowStartCondition is
the starting item of a new window. Thus, a given item may be found
in multiple windows drawn from the same binding sequence.
The following examples illustrate the use of sliding windows.
Show windows of three items.
for sliding window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when fn:true() only end at $e when $e - $s eq 2 return <window>{ $w }</window>
Result of the above query:
<window>2 4 6</window> <window>4 6 8</window> <window>6 8 10</window> <window>8 10 12</window> <window>10 12 14</window>
Show moving averages of three items.
for sliding window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when fn:true() only end at $e when $e - $s eq 2 return avg($w)
Result of the above query:
4 6 8 10 12
Show overlapping windows of up to three items (illustrates
end
clause without the only
keyword).
for sliding window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when fn:true() end at $e when $e - $s eq 2 return <window>{ $w }</window>
Result of the above query:
<window>2 4 6</window> <window>4 6 8</window> <window>6 8 10</window> <window>8 10 12</window> <window>10 12 14</window> <window>12 14</window> <window>14</window>
The effects of a window
clause on the tuple stream
are similar to the effects of a for
clause. As
described in 3.9.4 Window Clause,
a window
clause generates zero or more windows, each
of which is represented by at least one and at most nine bound
variables.
If the window
clause is the initial clause in a
FLWOR expression, the bound variables that describe each window
become an output tuple. These tuples form the initial tuple stream
that serves as input to the next clause of the FLWOR expression. If
ordering mode
is ordered
, the order of tuples in the tuple stream is
the order in which their start items appear in the binding
sequence; otherwise the order of the tuple stream is implementation-dependent. The
cardinality of the tuple stream is equal to the number of
windows.
If a window
clause is an intermediate clause in a
FLWOR expression, each input tuple generates zero or more output
tuples, each consisting of the original bound variables of the
input tuple plus the new bound variables that represent one of the
generated windows. For each tuple T in the input tuple
stream, the output tuple stream will contain NT
tuples, where NT is the number of windows
generated by the window
clause, given the bindings in
the input tuple T. Input tuples for which no windows are
generated are not represented in the output tuple stream. If
ordering mode
is ordered
, the order of tuples in the output stream
is determined primarily by the order of the input tuples from which
they were derived, and secondarily by the order in which their
start items appear in the binding sequence. If ordering mode is
unordered
, the order of tuples in the output stream is
implementation-dependent.
The following example illustrates a window
clause
that is the initial clause in a FLWOR expression. The example is
based on input data that consists of a sequence of closing stock
prices for a specific company. For this example we assume the
following input data (assume that the price
elements
have a validated type of xs:decimal
):
<stock> <closing> <date>2008-01-01</date> <price>105</price> </closing> <closing> <date>2008-01-02</date> <price>101</price> </closing> <closing> <date>2008-01-03</date> <price>102</price> </closing> <closing> <date>2008-01-04</date> <price>103</price> </closing> <closing> <date>2008-01-05</date> <price>102</price> </closing> <closing> <date>2008-01-06</date> <price>104</price> </closing> </stock>
A user wishes to find "run-ups," which are defined as sequences of dates that begin with a "low" and end with a "high" price (that is, the stock price begins to rise on the first day of the run-up, and continues to rise or remain even through the last day of the run-up.) The following query uses a tumbling window to find run-ups in the input data:
for tumbling window $w in //closing start $first next $second when $first/price < $second/price end $last next $beyond when $last/price > $beyond/price return <run-up> <start-date>{fn:data($first/date)}</start-date> <start-price>{fn:data($first/price)}</start-price> <end-date>{fn:data($last/date)}</end-date> <end-price>{fn:data($last/price)}</end-price> </run-up>
For our sample input data, this tumbling window
clause generates a tuple stream consisting of two tuples, each
representing a window and containing five bound variables named
$w
, $first
, $second
,
$last
, and $beyond
. The
return
clause is evaluated for each of these tuples,
generating the following query result:
<run-up> <start-date>2008-01-02</start-date> <start-price>101</start-price> <end-date>2008-01-04</start-date> <end-price>103</end-price> </run-up> <run-up> <start-date>2008-01-05</start-date> <start-price>102</start-price> <end-date>2008-01-06</start-date> <end-price>104</end-price> </run-up>
The following example illustrates a window
clause
that is an intermediate clause in a FLWOR expression. In this
example, the input data contains closing stock prices for several
different companies, each identified by a three-letter symbol. We
assume the following input data (again assuming that the type of
the price
element is xs:decimal
):
<stocks> <closing> <symbol>ABC</symbol> <date>2008-01-01</date> <price>105</price> </closing> <closing> <symbol>DEF</symbol> <date>2008-01-01</date> <price>057</price> </closing> <closing> <symbol>ABC</symbol> <date>2008-01-02</date> <price>101</price> </closing> <closing> <symbol>DEF</symbol> <date>2008-01-02</date> <price>054</price> </closing> <closing> <symbol>ABC</symbol> <date>2008-01-03</date> <price>102</price> </closing> <closing> <symbol>DEF</symbol> <date>2008-01-03</date> <price>056</price> </closing> <closing> <symbol>ABC</symbol> <date>2008-01-04</date> <price>103</price> </closing> <closing> <symbol>DEF</symbol> <date>2008-01-04</date> <price>052</price> </closing> <closing> <symbol>ABC</symbol> <date>2008-01-05</date> <price>101</price> </closing> <closing> <symbol>DEF</symbol> <date>2008-01-05</date> <price>055</price> </closing> <closing> <symbol>ABC</symbol> <date>2008-01-06</date> <price>104</price> </closing> <closing> <symbol>DEF</symbol> <date>2008-01-06</date> <price>059</price> </closing> </stocks>
As in the previous example, we want to find "run-ups," which are
defined as sequences of dates that begin with a "low" and end with
a "high" price for a specific company. In this example, however,
the input data consists of stock prices for multiple companies.
Therefore it is necessary to isolate the stock prices of each
company before forming windows. This can be accomplished by an
initial for
and let
clause, followed by a
window
clause, as follows:
for $symbol in fn:distinct-values(//symbol) let $closings := //closing[symbol = $symbol] for tumbling window $w in $closings start $first next $second when $first/price < $second/price end $last next $beyond when $last/price > $beyond/price return <run-up symbol="{$symbol}"> <start-date>{fn:data($first/date)}</start-date> <start-price>{fn:data($first/price)}</start-price> <end-date>{fn:data($last/date)}</end-date> <end-price>{fn:data($last/price)}</end-price> </run-up>
Note:
In the above example, the for
and let
clauses could be rewritten as follows:
for $closings in //closing let $symbol := $closings/symbol group by $symbol
The group by
clause is described in 3.9.7 Group By Clause.
The for
and let
clauses in this query
generate an initial tuple stream consisting of two tuples. In the
first tuple, $symbol
is bound to "ABC" and
$closings
is bound to the sequence of
closing
elements for company ABC. In the second tuple,
$symbol
is bound to "DEF" and $closings
is bound to the sequence of closing
elements for
company DEF.
The window
clause operates on this initial tuple
stream, generating two windows for the first tuple and two windows
for the second tuple. The result is a tuple stream consisting of
four tuples, each with the following bound variables:
$symbol
, $closings
, $w
,
$first
, $second
, $last
, and
$beyond
. The return
clause is then
evaluated for each of these tuples, generating the following query
result:
<run-up symbol="ABC"> <start-date>2008-01-02</start-date> <start-price>101</start-price> <end-date>2008-01-04</start-date> <end-price>103</end-price> </run-up> <run-up symbol="ABC"> <start-date>2008-01-05</start-date> <start-price>101</start-price> <end-date>2008-01-06</start-date> <end-price>104</end-price> </run-up> <run-up symbol="DEF"> <start-date>2008-01-02</start-date> <start-price>54</start-price> <end-date>2008-01-03</start-date> <end-price>56</end-price> </run-up> <run-up symbol="DEF"> <start-date>2008-01-04</start-date> <start-price>52</start-price> <end-date>2008-01-06</start-date> <end-price>59</end-price> </run-up>
[60] | WhereClause |
::= | "where" ExprSingle |
A where
clause serves as a filter for the tuples in
its input tuple stream. The expression in the where
clause, called the where-expression, is evaluated once for
each of these tuples. If the effective boolean value of the where-expression
is true
, the tuple is retained in the output tuple
stream; otherwise the tuple is discarded.
Examples:
This example illustrates the effect of a where
clause on a tuple stream:
Input tuple stream:
($a = 5, $b = 11) ($a = 91, $b = 42) ($a = 17, $b = 30) ($a = 85, $b = 63)
where
clause:
where $a > $b
Output tuple stream:
($a = 91, $b = 42) ($a = 85, $b = 63)
The following query illustrates how a where
clause
might be used with a positional variable to perform
sampling on an input sequence. The query returns one value out of
each one hundred input values.
for $x at $i in $inputvalues
where $i mod 100 = 0
return $x
[59] | CountClause |
::= | "count" "$" VarName |
The purpose of a count
clause is to enhance the
tuple stream with a new variable that is bound, in each tuple, to
the ordinal position of that tuple in the tuple stream. The name of
the new variable is specified in the count
clause.
The output tuple stream of a count
clause is the
same as its input tuple stream, with each tuple enhanced by one
additional variable that is bound to the ordinal position of that
tuple in the tuple stream. However, if the name of the new variable
is the same as the name of an existing variable in the input tuple
stream, the new variable occludes (replaces) the existing variable
of the same name, and the number of bound variables in each tuple
is unchanged.
The following examples illustrate uses of the count
clause:
This example illustrates the effect of a count
clause on an input tuple stream:
Input tuple stream:
($name = "Bob", $age = 21) ($name = "Carol", $age = 19) ($name = "Ted", $age = 20) ($name = "Alice", $age = 22)
count
clause:
count $counter
Output tuple stream:
($name = "Bob", $age = 21, $counter = 1) ($name = "Carol", $age = 19, $counter = 2) ($name = "Ted", $age = 20, $counter = 3) ($name = "Alice", $age = 22, $counter = 4)
This example illustrates how a counter might be used to filter
the result of a query. The query ranks products in order by
decreasing sales, and returns the three products with the highest
sales. Assume that the variable $products
is bound to
a sequence of product
elements, each of which has
name
and sales
child-elements.
for $p in $products order by $p/sales descending count $rank where $rank <= 3 return <product rank="{$rank}"> {$p/name, $p/sales} </product>
The result of this query has the following structure:
<product rank="1"> <name>Toaster</name> <sales>968</sales> </product> <product rank="2"> <name>Blender</name> <sales>520</sales> </product> <product rank="3"> <name>Can Opener</name> <sales>475</sales> </product>
[61] | GroupByClause |
::= | "group" "by" GroupingSpecList |
[62] | GroupingSpecList |
::= | GroupingSpec
("," GroupingSpec)* |
[63] | GroupingSpec |
::= | "$" VarName
("collation" URILiteral)? |
A group by
clause generates an output tuple stream
in which each tuple represents a group of tuples from the input
tuple stream. We will refer to the tuples in the input tuple stream
as pre-grouping tuples, and the tuples in the output tuple
stream as post-grouping tuples.
The post-grouping tuples have exactly the same variable-names as
the pre-grouping tuples. The number of post-grouping tuples is less
than or equal to the number of pre-grouping tuples. The group
by
clause assigns each pre-grouping tuple to a group, and
generates one post-grouping tuple for each group. Subsequent
clauses in the FLWOR expression see only the variable bindings in
the post-grouping tuples; they no longer have access to the
variable bindings in the pre-grouping tuples.
[Definition: A group by
clause
consists of the keywords group by
followed by one or
more variables called grouping variables.] The name of each
grouping variable must be equal (by the eq
operator on
expanded
QNames) to the name of a bound variable in the input tuple
stream; otherwise a static error is raised [err:XQST0094].
The process of group formation proceeds as follows:
[Definition: The atomized value of a grouping variable is called a grouping key.] For each pre-grouping tuple, the grouping keys are created by atomizing the values of the grouping variables. If the resulting value for any grouping variable consists of more than one item, a dynamic error is raised [err:XPTY0004].
The input tuple stream is partitioned into groups of tuples
whose grouping keys are equivalent. [Definition: Two tuples
T1 and T2 have equivalent grouping
keys if and only if, for each grouping variable GV,
the atomized value of GV in T1 is deep-equal
to the atomized value of GV in T2, as defined
by applying the function fn:deep-equal
using the
appropriate collation.] If these values are of different numeric
types, and differ from each other by small amounts, then the
deep-equal relationship is not transitive, because of rounding
effects occurring during type promotion. When comparing three
values A
, B
, and C
such that
A eq B
, B eq C
, but A ne C
,
then the number of items in the result of the function (as well as
the choice of which items are returned) is , subject only to the
constraints that (a) no two items in the result sequence compare
equal to each other, and (b) every input item that does not appear
in the result sequence compares equal to some item that does appear
in the result sequence. See Section
14.2.1 fn:distinct-values FO30 for
further discussion of this issue in a different context.
Note:
The atomized grouping key will always be either an empty
sequence or a single atomic value. Defining equivalence by
reference to the fn:deep-equal
function ensures that
the empty sequence is equivalent only to the empty sequence, that
NaN
is equivalent to NaN
, that
untypedAtomic values are compared as strings, and that values for
which the eq
operator is not defined are considered
non-equivalent.
The appropriate collation for comparing two grouping keys is the collation specified in the pertinent GroupingSpec if present, or the default collation from the static context otherwise. If the collation is specified by a relative URI, that relative URI is resolved to an absolute URI using the Static Base URI. If the specified collation is not found in statically known collations, a static error is raised [err:XQST0076].
Each group of tuples produced by the above process results in one post-grouping tuple. The pre-grouping tuples from which the group is derived have equivalent grouping keys, but these keys are not necessarily identical (for example, the strings "Frog" and "frog" might be equivalent according to the collation in use.) In the post-grouping tuple, each grouping variable is bound to the value of that variable in one of the pre-grouping tuples from which the group is derived. The choice of tuple is implementation-dependent.
Editorial note | |
Some members of the XQuery Working Group would prefer that the grouping variables in the post-grouping tuple contain the grouping key for a grouping variable in a pre-grouping tuple, which is atomized, rather than the value of the grouping variable in a pre-grouping tuple. We welcome feedback on this question. |
In the post-grouping tuple generated for a given group, each
non-grouping variable is bound to a sequence containing the
concatenated values of that variable in all the pre-grouping tuples
that were assigned to that group. If ordering mode is ordered
, the
values derived from individual tuples are concatenated in a way
that preserves the order of the pre-grouping tuple stream;
otherwise the ordering of these values is implementation-dependent.
Note:
This behavior may be surprising to SQL programmers, since SQL reduces the equivalent of a non-grouping variable to one representative value. Consider the following query:
let $x := 64000 for $c in //customer let $d := $c/department where $c/salary > $x group by $d return <department name="{$d}"> Number of employees earning more than ${$x} is {count($c)} </department>
If there are three qualifying customers in the sales department this evaluates to:
<department name="sales"> Number of employees earning more than $64000 64000 64000 is 3 </department>
In XQuery, each group is a sequence of items that match the
group by criteria—in a tree-structured language like XQuery, this
is convenient, because further structures can be built based on the
items in this sequence. Because there are three items in the group,
$x
evaluates to a sequence of three items. To reduce
this to one item, use fn:distinct-values()
:
let $x := 64000 for $c in //customer let $d := $c/department where $c/salary > $x group by $d return <department name="{$d}"> Number of employees earning more than ${distinct-values($x)} is {count($c)} </department>
Note:
In general, the static type of a variable in a post-grouping tuple is different from the static type of the variable with the same name in the pre-grouping tuples.
The order in which tuples appear in the post-grouping tuple stream is implementation-dependent.
Note:
An order by
clause can be used to impose a
value-based ordering on the post-grouping tuple stream. Similarly,
if it is desired to impose a value-based ordering within a group
(i.e., on the sequence of items bound to a non-grouping variable),
this can be accomplished by a nested FLWOR expression that iterates
over these items and applies an order by
clause. In
some cases, a value-based ordering within groups can be
accomplished by applying an order by
clause on a
non-grouping variable before applying the group by
clause.
A group by
clause rebinds all the variables in the
input tuple stream. The scopes of these variables are not affected
by the group by
clause, but in post-grouping tuples
the values of the variables represent group properties rather than
properties of individual pre-grouping tuples.
Examples:
This example illustrates the effect of a group by
clause on a tuple stream.
Input tuple stream:
($storeno = <storeno>S101</storeno>, $itemno = <itemno>P78395</itemno>) ($storeno = <storeno>S102</storeno>, $itemno = <itemno>P94738</itemno>) ($storeno = <storeno>S101</storeno>, $itemno = <itemno>P41653</itemno>) ($storeno = <storeno>S102</storeno>, $itemno = <itemno>P70421</itemno>)
group by
clause:
group by $storeno
Output tuple stream:
($storeno = <storeno>S101</storeno>, $itemno = (<itemno>P78395</itemno>, <itemno>P41653<itemno>)) ($storeno = <storeno>S102</storeno>, $itemno = (<itemno>P94738</itemno>, <itemno>P70421</itemno>))
This example and the ones that follow are based on two separate
sequences of elements, named $sales
and
$products
. We assume that the variable
$sales
is bound to a sequence of elements with the
following structure:
<sales> <storeno>S101</storeno> <itemno>P78395</itemno> <qty>125</qty> </sales>
We also assume that the variable $products
is bound
to a sequence of elements with the following structure:
<product> <itemno>P78395</itemno> <price>25.00</price> <category>Men's Wear</category> </product>
The simplest kind of grouping query has a single grouping variable. The query in this example finds the total quantity of items sold by each store:
for $s in $sales let $storeno := $s/storeno group by $storeno return <store number="{$storeno}" total-qty="{sum($s/qty)}"/>
The result of this query is a sequence of elements with the following structure:
<store number="S101" total-qty="1550" /> <store number="S102" total-qty="2125" />
In a more realistic example, a user might be interested in the total revenue generated by each store for each product category. Revenue depends on both the quantity sold of various items and the price of each item. The following query joins the two input sequences and groups the resulting tuples by two grouping variables:
for $s in $sales, $p in $products[itemno = $s/itemno] let $storeno := $s/storeno, $category := $p/category, $revenue := $s/qty * $p/price group by $storeno, $category return <summary storeno="{$storeno}" category="{$category}" revenue="{sum($revenue)}"/>
The result of this query is a sequence of elements with the following structure:
<summary storeno="S101" category="Men's Wear" revenue="10185"/> <summary storeno="S101" category="Stationery" revenue="4520"/> <summary storeno="S102" category="Men's Wear" revenue="9750"/> <summary storeno="S102" category="Appliances" revenue="22650"/> <summary storeno="S102" category="Jewelry" revenue="30750"/>
The result of the previous example was a "flat" list of elements. A user might prefer the query result to be presented in the form of a hierarchical report, grouped primarily by store (in order by store number) and secondarily by product category. Within each store, the user might want to see only those product categories whose total revenue exceeds $10,000, presented in descending order by their total revenue. This report is generated by the following query:
for $s1 in $sales let $storeno := $s1/storeno group by $storeno order by $storeno return <store storeno="{$storeno}"> {for $s2 in $s1, $p in $products[itemno = $s2/itemno] let $category := $p/category, $revenue := $s2/qty * $p/price group by $category let $group-revenue := sum($revenue) where $group-revenue > 10000 order by $group-revenue descending return <category name="{$category}" revenue="{$group-revenue}"/> } </store>
The result of this example query has the following structure:
<store storeno="S101"> <category name="Men's Wear" revenue="10185"/> </store> <store storeno="S102"> <category name="Jewelry" revenue="30750"/> <category name="Appliances" revenue="22650"/> </store>
The following example illustrates how to avoid a possible pitfall in writing grouping queries.
In each post-grouping tuple, all variables except for the
grouping variable are bound to sequences of items derived from all
the pre-grouping tuples from which the group was formed. For
instance, in the following query, $high-price
is bound
to a sequence of items in the post-grouping tuple.
let $high-price := 1000 for $p in $products[price > $high-price] let $category := $p/category group by $category return <category name="{$category}"> {fn:count($p)} products have price greater than {$high-price}. </category>
If three products in the "Men's Wear" category have prices greater than 1000, the result of this query might look (in part) like this:
<category name="Men's Wear"> 3 products have price greater than 1000 1000 1000. </category>
The repetition of "1000" in this query result is due to the fact
that $high-price
is not a grouping variable. One way to
avoid this repetition is to move the binding of
$high-price
to an outer-level FLWOR expression, as
follows:
let $high-price := 1000 return for $p in $products[price > $high-price] let $category := $p/category group by $category return <category name="{$category}"> {fn:count($p)} products have price greater than {$high-price}. </category>
The result of the revised query might contain the following element:
<category name="Men's Wear"> 3 products have price greater than 1000. </category>
[64] | OrderByClause |
::= | (("order" "by") | ("stable" "order" "by")) OrderSpecList |
[65] | OrderSpecList |
::= | OrderSpec (","
OrderSpec)* |
[66] | OrderSpec |
::= | ExprSingle
OrderModifier |
[67] | OrderModifier |
::= | ("ascending" | "descending")? ("empty" ("greatest" |
"least"))? ("collation" URILiteral)? |
The purpose of an order by
clause is to impose a
value-based ordering on the tuples in the tuple stream. The output
tuple stream of the order by
clause contains the same
tuples as its input tuple stream, but the tuples may be in a
different order.
An order by
clause contains one or more ordering
specifications, called orderspecs, as shown in the grammar.
For each tuple in the input tuple stream, the orderspecs are
evaluated, using the variable bindings in that tuple. The relative
order of two tuples is determined by comparing the values of their
orderspecs, working from left to right until a pair of unequal
values is encountered. If an orderspec specifies a collation, that collation is
used in comparing values of type xs:string
,
xs:anyURI
, or types derived from them (otherwise, the
default
collation is used in comparing values of these types). If an
orderspec specifies a collation by a relative URI, that relative
URI is resolved
to an absolute URI using the Static Base URI. If an
orderspec specifies a collation that is not found in statically known collations, an error
is raised [err:XQST0076].
The process of evaluating and comparing the orderspecs is based on the following rules:
Atomization is applied to the result of the expression in each orderspec. If the result of atomization is neither a single atomic value nor an empty sequence, a type error is raised [err:XPTY0004].
If the value of an orderspec has the dynamic type
xs:untypedAtomic
(such as character data in a
schemaless document), it is cast to the type
xs:string
.
Note:
Consistently treating untyped values as strings enables the sorting process to begin without complete knowledge of the types of all the values to be sorted.
All the non-empty orderspec values must be convertible to a
common type by subtype substitution and/or
type
promotion. The ordering is performed in the least common type
that has a gt
operator. If two or more non-empty
orderspec values are not convertible to a common type that has a
gt
operator, a type error is raised [err:XPTY0004].
Example: The orderspec values include a value of type
hatsize
, which is derived from
xs:integer
, and a value of type shoesize
,
which is derived from xs:decimal
. The least common
type reachable by subtype substitution and type promotion is
xs:decimal
.
Example: The orderspec values include a value of type
xs:string
and a value of type xs:anyURI
.
The least common type reachable by subtype substitution and type
promotion is xs:string
.
For the purpose of determining their relative position in the ordering sequence, the greater-than relationship between two orderspec values W and V is defined as follows:
When the orderspec specifies empty least
, the
following rules are applied in order:
If V is an empty sequence and W is not an empty sequence, then W greater-than V is true.
If V is NaN
and W is neither
NaN
nor an empty sequence, then W
greater-than V is true.
If a specific collation C is specified, and V
and W are both of type xs:string
or are
convertible to xs:string
by subtype
substitution and/or type promotion, then:
If fn:compare(V, W, C)
is less than zero, then
W greater-than V is true; otherwise
W greater-than V is false.
If none of the above rules apply, then:
If W gt V
is true, then W
greater-than V is true; otherwise W
greater-than V is false.
When the orderspec specifies empty greatest
, the
following rules are applied in order:
If W is an empty sequence and V is not an empty sequence, then W greater-than V is true.
If W is NaN
and V is neither
NaN
nor an empty sequence, then W
greater-than V is true.
If a specific collation C is specified, and V
and W are both of type xs:string
or are
convertible to xs:string
by subtype
substitution and/or type promotion, then:
If fn:compare(V, W, C)
is less than zero, then
W greater-than V is true; otherwise
W greater-than V is false.
If none of the above rules apply, then:
If W gt V
is true, then W
greater-than V is true; otherwise W
greater-than V is false.
When the orderspec specifies neither empty least
nor empty greatest
, the default order for empty sequences in
the static
context determines whether the rules for empty
least
or empty greatest
are used.
If T1 and T2 are two tuples in the input tuple stream, and V1 and V2 are the first pair of values encountered when evaluating their orderspecs from left to right for which one value is greater-than the other (as defined above), then:
If V1 is greater-than V2: If the
orderspec specifies descending
, then T1
precedes T2 in the output tuple stream; otherwise,
T2 precedes T1 in the output tuple stream.
If V2 is greater-than V1: If the
orderspec specifies descending
, then T2
precedes T1 in the output tuple stream; otherwise,
T1 precedes T2 in the output tuple stream.
If neither V1 nor V2 is greater-than the other for any pair of orderspecs for tuples T1 and T2, the following rules apply.
If stable
is specified, the original order of
T1 and T2 is preserved in the output tuple
stream.
If stable
is not specified, the order of
T1 and T2 in the output tuple stream is implementation-dependent.
Note:
If two orderspecs return the special floating-point values
positive and negative zero, neither of these values is
greater-than the other, since +0.0 gt -0.0
and -0.0 gt +0.0
are both false
.
Examples:
This example illustrates the effect of an order by
clause on a tuple stream. The keyword stable
indicates
that, when two tuples have equal sort keys, their order in the
input tuple stream is preserved.
Input tuple stream:
($license = "PFQ519", $make = "Ford", $value = 16500) ($license = "HAJ865", $make = "Honda", $value = 22750) ($license = "NKV473", $make = "Ford", $value = 21650) ($license = "RCM922", $make = "Dodge", $value = 11400) ($license = "ZBX240", $make = "Ford", $value = 16500) ($license = "KLM030", $make = "Dodge", $value = () )
order by
clause:
stable order by $make, $value descending empty least
Output tuple stream:
($license = "RCM922", $make = "Dodge", $value = 11400) ($license = "KLM030", $make = "Dodge", $value = () ) ($license = "NKV473", $make = "Ford", $value = 21650) ($license = "PFQ519", $make = "Ford", $value = 16500) ($license = "ZBX240", $make = "Ford", $value = 16500) ($license = "HAJ865", $make = "Honda", $value = 22750)
The following example shows how an order by
clause
can be used to sort the result of a query, even if the sort key is
not included in the query result. This query returns employee names
in descending order by salary, without returning the actual
salaries:
for $e in $employees order by $e/salary descending return $e/name
Note:
Since the order by
clause in a FLWOR expression is
the only facility provided by XQuery for specifying a value
ordering, a FLWOR expression must be used in some queries where
iteration would not otherwise be necessary. For example, a list of
books with price less than 100 might be obtained by a simple
path
expression such as $books/book[price < 100]
.
But if these books are to be returned in alphabetic order by title,
the query must be expressed as follows:
for $b in $books/book[price < 100] order by $b/title return $b
[68] | ReturnClause |
::= | "return" ExprSingle |
The return
clause is the final clause of a FLWOR
expression. The return
clause is evaluated once for
each tuple in its input tuple stream, using the variable bindings
in the respective tuples, in the order in which these tuples appear
in the input tuple stream. The results of these evaluations are
concatenated, as if by the comma operator, to form the result of the
FLWOR expression.
The following example illustrates a FLWOR expression containing
several clauses. The for
clause iterates over all the
departments in an input document named depts.xml
,
binding the variable $d
to each department in turn.
For each binding of $d
, the let
clause
binds variable $e
to all the employees in the given
department, selected from another input document named
emps.xml
(the relationship between employees and
departments is represented by matching their deptno
values). Each tuple in the resulting tuple stream contains a pair
of bindings for $d
and $e
($d
is bound to a department and $e
is
bound to a set of employees in that department). The
where
clause filters the tuple stream, retaining only
those tuples that represent departments having at least ten
employees. The order by
clause orders the surviving
tuples in descending order by the average salary of the employees
in the department. The return
clause constructs a new
big-dept
element for each surviving tuple, containing
the department number, headcount, and average salary.
for $d in fn:doc("depts.xml")//dept let $e := fn:doc("emps.xml")//emp[deptno eq $d/deptno] where fn:count($e) >= 10 order by fn:avg($e/salary) descending return <big-dept> { $d/deptno, <headcount>{fn:count($e)}</headcount>, <avgsal>{fn:avg($e/salary)}</avgsal> } </big-dept>
Notes:
The order in which items appear in the result of a FLWOR
expression depends on the ordering of the input tuple stream to the
return
clause, which in turn is influenced by
order by
clauses and by ordering mode. For example, consider the
following query, which is based on the same two input documents as
the previous example:
for $d in fn:doc("depts.xml")//dept order by $d/deptno for $e in fn:doc("emps.xml")//emp[deptno eq $d/deptno] return <assignment> {$d/deptno, $e/name} </assignment>
The result of this query is a sequence of
assignment
elements, each containing a
deptno
element and a name
element. The
sequence will be ordered primarily by the deptno
values because of the order by
clause. If ordering mode is
ordered
, subsequences of assignment
elements with equal deptno
values will be ordered by
the document order of their name
elements within the
emps.xml
document; otherwise the ordering of these
subsequences will be implementation-dependent.
Parentheses are helpful in return
clauses that
contain comma operators, since FLWOR expressions have a higher
precedence than the comma operator. For example, the following
query raises an error because after the comma, $j
is
no longer within the FLWOR expression, and is an undefined
variable:
let $i := 5, $j := 20 * $i return $i, $j
Parentheses can be used to bring $j
into the
return
clause of the FLWOR expression, as the
programmer probably intended:
let $i := 5, $j := 20 * $i return ($i, $j)
[128] | OrderedExpr |
::= | "ordered" "{" Expr
"}" |
[129] | UnorderedExpr |
::= | "unordered" "{" Expr
"}" |
The purpose of ordered
and unordered
expressions is to set the ordering mode in the static context to
ordered
or unordered
for a certain region
in a query. The specified ordering mode applies to the expression
nested inside the curly braces. For expressions where the ordering
of the result is not significant, a performance advantage may be
realized by setting the ordering mode to unordered
,
thereby granting the system flexibility to return the result in the
order that it finds most efficient.
Ordering
mode affects the behavior of path expressions that include a
"/
" or "//
" operator or an axis step; union
,
intersect
, and except
expressions; the
fn:id
, fn:element-with-id
,
and fn:idref
functions; and certain clauses within a
FLWOR expression. If ordering mode is ordered
, node
sequences returned by path expressions, union
,
intersect
, and except
expressions, and
the fn:id
and fn:idref
functions are in
document
order; otherwise the order of these return sequences is
implementation-dependent. The
effect of ordering mode on FLWOR expressions is described in
3.9.2 For Clause,
3.9.4.3 Effects of
Window Clauses on the Tuple Stream, and 3.9.7 Group By Clause. Ordering mode has
no effect on duplicate elimination.
Note:
In a region of a query where ordering mode is
unordered
, the result of an expression may be
nondeterministic if the expression invokes certain functions that
are affected by the ordering of node sequences. These functions
include fn:position
, fn:last
,
fn:index-of
, fn:insert-before
,
fn:remove
, fn:reverse
, and
fn:subsequence
. The functions
fn:boolean
and fn:not
are
nondeterministic if ordering mode is unordered
and the
argument contains at least one node and at least one atomic value
(see 2.4.3 Effective Boolean
Value). Also, within a path expression in an unordered
region, numeric predicates are
nondeterministic. For example, in an ordered region, the path
expression (//a/b)[5]
will return the fifth qualifying
b
-element in document order. In an unordered region,
the same expression will return an implementation-dependent
qualifying b
-element.
Note:
The fn:id
and fn:idref
functions are
described in [XQuery and XPath
Functions and Operators 3.0] as returning their results in
document
order. Since ordering mode is a feature of XQuery, relaxation
of the ordering requirement for function results when ordering mode
is unordered
is a feature of XQuery rather than of the
functions themselves.
The use of an unordered
expression is illustrated
by the following example, which joins together two documents named
parts.xml
and suppliers.xml
. The example
returns the part numbers of red parts, paired with the supplier
numbers of suppliers who supply these parts. If an
unordered
expression were not used, the resulting list
of (part number, supplier number) pairs would be required to have
an ordering that is controlled primarily by the document order of
parts.xml
and secondarily by the document order of
suppliers.xml
. However, this might not be the most
efficient way to process the query if the ordering of the result is
not important. An XQuery implementation might be able to process
the query more efficiently by using an index to find the red parts,
or by using suppliers.xml
rather than
parts.xml
to control the primary ordering of the
result. The unordered
expression gives the query
evaluator freedom to make these kinds of optimizations.
unordered { for $p in fn:doc("parts.xml")/parts/part[color = "Red"], $s in fn:doc("suppliers.xml")/suppliers/supplier where $p/suppno = $s/suppno return <ps> { $p/partno, $s/suppno } </ps> }
In addition to ordered
and unordered
expressions, XQuery provides a function named
fn:unordered
that operates on any sequence of items
and returns the same sequence in a nondeterministic order. A call
to the fn:unordered
function may be thought of as
giving permission for the argument expression to be materialized in
whatever order the system finds most efficient. The
fn:unordered
function relaxes ordering only for the
sequence that is its immediate operand, whereas an
unordered
expression sets the ordering mode for its operand
expression and all nested expressions.
XQuery 3.0 supports a conditional expression based on the
keywords if
, then
, and
else
.
[76] | IfExpr |
::= | "if" "(" Expr ")" "then"
ExprSingle "else" ExprSingle |
The expression following the if
keyword is called
the test expression, and the expressions following the
then
and else
keywords are called the
then-expression and else-expression,
respectively.
The first step in processing a conditional expression is to find the effective boolean value of the test expression, as defined in 2.4.3 Effective Boolean Value.
The value of a conditional expression is defined as follows: If
the effective boolean value of the test expression is
true
, the value of the then-expression is returned. If
the effective boolean value of the test expression is
false
, the value of the else-expression is
returned.
Conditional expressions have a special rule for propagating
dynamic
errors. If the effective value of the test expression is
true
, the conditional expression ignores (does not
raise) any dynamic errors encountered in the else-expression. In
this case, since the else-expression can have no observable effect,
it need not be evaluated. Similarly, if the effective value of the
test expression is false
, the conditional expression
ignores any dynamic errors encountered in the
then-expression, and the then-expression need not be evaluated.
Here are some examples of conditional expressions:
In this example, the test expression is a comparison expression:
if ($widget1/unit-cost < $widget2/unit-cost) then $widget1 else $widget2
In this example, the test expression tests for the existence of
an attribute named discounted
, independently of its
value:
if ($part/@discounted) then $part/wholesale else $part/retail
[70] | SwitchExpr |
::= | "switch" "(" Expr ")"
SwitchCaseClause+
"default" "return" ExprSingle |
[71] | SwitchCaseClause |
::= | ("case" SwitchCaseOperand)+ "return"
ExprSingle |
[72] | SwitchCaseOperand |
::= | ExprSingle |
The switch expression chooses one of several expressions to evaluate based on the input value.
In a switch
expression, the switch
keyword is followed by an expression enclosed in parentheses,
called the switch operand expression. This is the expression
whose value is being compared. The remainder of the
switch
expression consists of one or more
case
clauses, with one or more case operand
expressions
each, and a default
clause.
The first step in evaluating a switch expression is to apply atomization to the value of the switch operand expression. If the result is a sequence of length greater than one, a type error is raised [err:XPTY0004].
The resulting value is matched against each SwitchCaseOperand in turn until a match is found or the list is exhausted. The matching is performed as follows:
The SwitchCaseOperand is evaluated.
The resulting value is atomized.
If the atomized sequence has length greater than one, a type error is raised [err:XPTY0004].
The atomized value of the switch operand expression is compared
with the atomized value of the SwitchCaseOperand using the
fn:deep-equal
function, with the default collation
from the static context.
[Definition: The effective case of a switch expression is the first case clause that matches, using the rules given above, or the default clause if no such case clause exists.] The value of the switch expression is the value of the return expression in the effective case.
Switch expressions have rules regarding the propagation of dynamic errors that take precedence over the general rules given in 2.3.4 Errors and Optimization. The return clauses of a switch expression must not raise any dynamic errors except in the effective case. Dynamic errors raised in the operand expressions of the switch or the case clauses are propagated; however, an implementation must not raise dynamic errors in the operand expressions of case clauses that occur after the effective case. An implementation is permitted to raise dynamic errors in the operand expressions of case clauses that occur before the effective case, but not required to do so.
The following example shows how a switch expression might be used:
switch ($animal) case "Cow" return "Moo" case "Cat" return "Meow" case "Duck" return "Quack" default return "What's that odd noise?"
Quantified expressions support existential and universal
quantification. The value of a quantified expression is always
true
or false
.
[69] | QuantifiedExpr |
::= | ("some" | "every") "$" VarName TypeDeclaration? "in" ExprSingle ("," "$" VarName TypeDeclaration? "in" ExprSingle)* "satisfies" ExprSingle |
[164] | TypeDeclaration |
::= | "as" SequenceType |
A quantified expression begins with a quantifier,
which is the keyword some
or every
,
followed by one or more in-clauses that are used to bind variables,
followed by the keyword satisfies
and a test
expression. Each in-clause associates a variable with an expression
that returns a sequence of items, called the binding sequence for
that variable. The in-clauses generate tuples of variable bindings,
including a tuple for each combination of items in the binding
sequences of the respective variables. Conceptually, the test
expression is evaluated for each tuple of variable bindings.
Results depend on the effective boolean value of the test expressions, as
defined in 2.4.3 Effective Boolean
Value. The value of the quantified expression is defined by
the following rules:
If the quantifier is some
, the quantified
expression is true
if at least one evaluation of the
test expression has the effective boolean value true
; otherwise
the quantified expression is false
. This rule implies
that, if the in-clauses generate zero binding tuples, the value of
the quantified expression is false
.
If the quantifier is every
, the quantified
expression is true
if every evaluation of the test
expression has the effective boolean value true
; otherwise
the quantified expression is false
. This rule implies
that, if the in-clauses generate zero binding tuples, the value of
the quantified expression is true
.
The scope of a variable bound in a quantified expression comprises all subexpressions of the quantified expression that appear after the variable binding. The scope does not include the expression to which the variable is bound.
Each variable bound in an in-clause of a quantified expression may have an optional type declaration. If the type of a value bound to the variable does not match the declared type according to the rules for SequenceType matching, a type error is raised [err:XPTY0004].
The order in which test expressions are evaluated for the
various binding tuples is implementation-dependent. If the
quantifier is some
, an implementation may return
true
as soon as it finds one binding tuple for which
the test expression has an effective boolean value of true
, and it
may raise a dynamic error as soon as it finds one
binding tuple for which the test expression raises an error.
Similarly, if the quantifier is every
, an
implementation may return false
as soon as it finds
one binding tuple for which the test expression has an effective boolean
value of false
, and it may raise a dynamic error as soon
as it finds one binding tuple for which the test expression raises
an error. As a result of these rules, the value of a quantified
expression is not deterministic in the presence of errors, as
illustrated in the examples below.
Here are some examples of quantified expressions:
This expression is true
if every part
element has a discounted
attribute (regardless of the
values of these attributes):
every $part in /parts/part satisfies $part/@discounted
This expression is true
if at least one
employee
element satisfies the given comparison
expression:
some $emp in /emps/employee satisfies ($emp/bonus > 0.25 * $emp/salary)
In the following examples, each quantified expression evaluates
its test expression over nine tuples of variable bindings, formed
from the Cartesian product of the sequences (1, 2, 3)
and (2, 3, 4)
. The expression beginning with
some
evaluates to true
, and the
expression beginning with every
evaluates to
false
.
some $x in (1, 2, 3), $y in (2, 3, 4) satisfies $x + $y = 4
every $x in (1, 2, 3), $y in (2, 3, 4) satisfies $x + $y = 4
This quantified expression may either return true
or raise a type
error, since its test expression returns true
for
one variable binding and raises a type error for another:
some $x in (1, 2, "cat") satisfies $x * 2 = 4
This quantified expression may either return false
or raise a type
error, since its test expression returns false
for
one variable binding and raises a type error for another:
every $x in (1, 2, "cat") satisfies $x * 2 = 4
This quantified expression contains a type declaration that is not
satisfied by every item in the test expression. If the Static
Typing Feature is implemented, this expression raises a
type error during
the static analysis phase. Otherwise, the
expression may either return true
or raise a type error during the
dynamic evaluation phase.
some $x as xs:integer in (1, 2, "cat") satisfies $x * 2 = 4
The try/catch expression provides error handling for dynamic
errors and type errors raised during dynamic evaluation, including
errors raised by the XQuery implementation and errors explicitly
raised in a query using the fn:error()
function.
[77] | TryCatchExpr |
::= | TryClause CatchClause+ |
[78] | TryClause |
::= | "try" "{" TryTargetExpr "}" |
[79] | TryTargetExpr |
::= | Expr |
[80] | CatchClause |
::= | "catch" CatchErrorList "{" Expr "}" |
[81] | CatchErrorList |
::= | NameTest ("|"
NameTest)* |
A try/catch expression catches dynamic errors and type errors raised during dynamic
evaluation for expressions that are lexically contained within the
try
clause. If the target expression does not raise a
dynamic error or a type error, the result of the try/catch
expression is the result of the target expression.
If the target expression raises a dynamic error or a type error,
the result of the try/catch expression is obtained by evaluating
the first catch
clause that "matches" the error value,
as described below. A catch
clause with one or more
NameTests matches any error whose error code matches one of these
NameTests. For instance, if the error code is
err:FOER0000
, then it matches a catch
clause whose ErrorList is err:FOER0000 | err:FOER0001
.
Wildcards may be used in NameTests; thus, the error code
err:FOER0000
also matches a catch
clause
whose ErrorList is err:*
or *:FOER0000
or
*
.
Within the scope of the catch
clause, a number of
variables are implicitly declared, giving information about the
error that occurred. These variables are initialized as described
in the following table:
Variable | Type | Value |
---|---|---|
err:code | xs:QName | The error code |
err:description | xs:string? | A description of the error condition; an
empty sequence if no description is available (for example, if the
error function was called with one
argument). |
err:value | item()* | Value associated with the error. For an error
raised by calling the error function, this is the
value of the third argument (if supplied). |
err:module | xs:string? | The URI (or system ID) of the query module containing the instruction where the error occurred, or an empty sequence if the information is not available. |
err:line-number | xs:integer? | The line number within the stylesheet module of the instruction where the error occurred, or an empty sequence if the information is not available. The value may be approximate. |
err:column-number | xs:integer? | The column number within the stylesheet module of the instruction where the error occurred, or an empty sequence if the information is not available. The value may be approximate. |
Try/catch expressions have a special rule for propagating dynamic errors. The try/catch expression ignores any dynamic errors encountered in catch clauses other than the first catch clause that matches an error raised by the try clause, and these catch clause expressions need not be evaluated.
Static errors are not caught by the try/catch expression.
If a function call occurs within a try
clause,
errors raised by evaluating the corresponding function are caught
by the try/catch expression. If a variable reference is used in a
try
clause, errors raised by binding a value to the
variable are not caught unless the binding expression occurs within
the try
clause.
Note:
The presence of a try/catch expression does not prevent an implementation from using a lazy evaluation strategy, nor does it prevent an optimizer performing expression rewrites. However, if the evaluation of an expression inside a try/catch is rewritten or deferred in this way, it must take its try/catch context with it. Similarly, expressions that were written outside the try/catch expression may be evaluated inside the try/catch, but only if they retain their original try/catch behavior. The presence of a try/catch does not change the rules that allow the processor to evaluate expressions in such a way that may avoid the detection of some errors.
Here are some examples of try/catch expressions.
A try/catch expression without a CatchErrorList catches any error:
try { $x cast as xs:integer } catch * { 0 }
The CatchErrorList in this try/catch expression specifies that
only err:FORG0001
is caught:
try { $x cast as xs:integer } catch err:FORG0001 { 0 }
The CatchErrorList in this try/catch expression specifies that
errors err:FORG0001
and err:XPTY0004
are
caught:
try { $x cast as xs:integer } catch err:FORG0001 | err:XPTY0004 { 0 }
Note:
In some implementations, err:XPTY0004
is detected
during static evaluation; it can only be caught if it is raised
during dynamic evaluation.
This try/catch expression shows how to return information about the error using implicitly defined error variables. Since the CatchErrorList is a wildcard, it catches any error:
try { fn:error(fn:QName('http://www.w3.org/2005/xqt-errors', 'err:FOER0000')) } catch * { $err:code, $err:value, " module: ", $err:module, "(", $err:line-number, ",", $err:column-number, ")" }
Errors raised by using the result of a try/catch expression are
not caught, since they are outside the scope of the
try
expression.
declare function local:thrice($x as xs:integer) as xs:integer { 3*$x }; local:thrice(try { "oops" } catch * { 3 } )
In this example, the try block succeeds, returning the string "oops", which is not a valid argument to the function.
In addition to their use in function
parameters and results, sequence types are used in instance
of
, typeswitch
,
cast
, castable
, and treat
expressions.
[90] | InstanceofExpr |
::= | TreatExpr (
"instance" "of" SequenceType )? |
The boolean operator instance of
returns
true
if the value of its first operand matches the
SequenceType in its second
operand, according to the rules for SequenceType matching; otherwise it
returns false
. For example:
5 instance of xs:integer
This example returns true
because the given value
is an instance of the given type.
5 instance of xs:decimal
This example returns true
because the given value
is an integer literal, and xs:integer
is derived by
restriction from xs:decimal
.
<a>{5}</a> instance of xs:integer
This example returns false
because the given value
is an element rather than an integer.
(5, 6) instance of xs:integer+
This example returns true
because the given
sequence contains two integers, and is a valid instance of the
specified type.
. instance of element()
This example returns true
if the context item is an
element node or false
if the context item is defined
but is not an element node. If the context item is undefined, a
dynamic error
is raised [err:XPDY0002].
[73] | TypeswitchExpr |
::= | "typeswitch" "(" Expr
")" CaseClause+ "default"
("$" VarName)? "return"
ExprSingle |
[74] | CaseClause |
::= | "case" ("$" VarName
"as")? SequenceTypeUnion "return"
ExprSingle |
[75] | SequenceTypeUnion |
::= | SequenceType
("|" SequenceType)* |
The typeswitch expression chooses one of several expressions to evaluate based on the dynamic type of an input value.
In a typeswitch
expression, the
typeswitch
keyword is followed by an expression
enclosed in parentheses, called the operand expression. This
is the expression whose type is being tested. The remainder of the
typeswitch
expression consists of one or more
case
clauses and a default
clause.
Each case
clause specifies one or
more SequenceTypes
followed by a return
expression. [Definition: The effective case in a
typeswitch
expression is the first case
clause in which the value of the operand expression matches a
SequenceType in the
SequenceTypeUnion of the
case
clause, using the rules of SequenceType matching. ] The value
of the typeswitch
expression is the value of the
return
expression in the effective case. If the value
of the operand expression does not match any SequenceType named in a
case
clause, the value of the typeswitch
expression is the value of the return
expression in
the default
clause.
In a case
or default
clause, if the
value to be returned depends on the value of the operand
expression, the clause must specify a variable name. Within the
return
expression of the case
or
default
clause, this variable name is bound to the
value of the operand expression. Inside a case
clause,
the static type
of the variable is the union of the SequenceTypes named in the
SequenceTypeUnion. Inside
a default
clause, the static type of the variable is
the same as the static type of the operand expression. If the value
to be returned by a case
or default
clause does not depend on the value of the operand expression, the
clause need not specify a variable.
The scope of a variable binding in a case
or
default
clause comprises that clause. It is not an
error for more than one case
or default
clause in the same typeswitch
expression to bind
variables with the same name.
A special rule applies to propagation of dynamic errors by
typeswitch
expressions. A typeswitch
expression ignores (does not raise) any dynamic errors encountered
in case
clauses other than the effective case.
Dynamic errors encountered in the default
clause are
raised only if there is no effective case. An implementation is
permitted to raise dynamic errors in the operand expressions of
case clauses that occur before the effective case, but not required to do
so.
The following example shows how a
typeswitch
expression might be used to process an
expression in a way that depends on its dynamic type.
typeswitch($customer/billing-address) case $a as element(*, USAddress) return $a/state case $a as element(*, CanadaAddress) return $a/province case $a as element(*, JapanAddress) return $a/prefecture default return "unknown"
The following example shows a union of sequence types in a single case:
typeswitch($customer/billing-address) case $a as element(*, USAddress) | element(*, AustraliaAddress) | element(*, MexicoAddress) return $a/state case $a as element(*, CanadaAddress) return $a/province case $a as element(*, JapanAddress) return $a/prefecture default return "unknown"
[93] | CastExpr |
::= | UnaryExpr ( "cast"
"as" SingleType
)? |
[163] | SingleType |
::= | AtomicOrUnionType
"?"? |
[168] | AtomicOrUnionType |
::= | EQName |
Occasionally it is necessary to convert a value to a specific
datatype. For this purpose, XQuery 3.0 provides a cast
expression that creates a new value of a specific type based on an
existing value. A cast
expression takes two operands:
an input expression and a target type. The type of
the input expression is called the input type. The target
type must be an atomic type that is in the in-scope schema
types [err:XPST0051]. In addition, the target type
cannot be xs:NOTATION
or xs:anyAtomicType
[err:XPST0080]. The
optional occurrence indicator "?
" denotes that an
empty sequence is permitted. If the target type has no namespace
prefix, it is considered to be in the default
element/type namespace. The semantics of the cast
expression are as follows:
The input expression is evaluated.
If the result contains a node, and the target type is namespace-sensitive, a type error [err:XPTY0117] is raised.
Note:
Casting a node to xs:QName
is not allowed because
it would be inappropriate to use the static context of the cast
expression to provide the namespace bindings for this operation.
Instead, use the fn:QName
function, which allows the
namespace context to be taken from the document containing the
QName.
The result of the first step is atomized.
If the result of atomization is a sequence of more than one atomic value, a type error is raised [err:XPTY0004].
If the result of atomization is an empty sequence:
If ?
is specified after the target type, the result
of the cast
expression is an empty sequence.
If ?
is not specified after the target type, a
type error is
raised [err:XPTY0004].
If the result of atomization is a single atomic value, the result of the cast expression depends on the input type and the target type. In general, the cast expression attempts to create a new value of the target type based on the input value. Only certain combinations of input type and target type are supported. A summary of the rules are listed below—the normative definition of these rules is given in [XQuery and XPath Functions and Operators 3.0]. For the purpose of these rules, an implementation may determine that one type is derived by restriction from another type either by examining the in-scope schema definitions or by using an alternative, implementation-dependent mechanism such as a data dictionary.
cast
is supported for the combinations of input
type and target type listed in
Section 18.1 Casting from primitive types to primitive types
FO30. For each of these combinations,
both the input type and the target type are primitive schema types. For example,
a value of type xs:string
can be cast into the schema
type xs:decimal
. For each of these built-in
combinations, the semantics of casting are specified in [XQuery and XPath Functions and Operators
3.0].
cast
is supported if the input type is a
non-primitive atomic type that is derived by restriction from the
target type. In this case, the input value is mapped into the value
space of the target type, unchanged except for its type. For
example, if shoesize
is derived by restriction from
xs:integer
, a value of type shoesize
can
be cast into the schema type xs:integer
.
cast
is supported if the target type is a
non-primitive atomic type and the input type is
xs:string
or xs:untypedAtomic
. The input
value is first converted to a value in the lexical space of the
target type by applying the whitespace normalization rules for the
target type (as defined in [XML Schema
1.0] or [XML Schema 1.1]). The
lexical value is then converted to the value space of the target
type using the schema-defined rules for the target type. If the
input value fails to satisfy some facet of the target type, a
dynamic error
may be raised as specified in [XQuery
and XPath Functions and Operators 3.0].
cast
is supported if the target type is a union
type and the input type is xs:string
or
xs:untypedAtomic
. The semantics of casting to a union
type are based on the rules for validation in [XML Schema 1.0] or [XML
Schema 1.1].
The effect of casting a string S to a union type U is the same as constructing an element or attribute node whose string value is S, validating it using U as the governing type, and atomizing the resulting node. The result will always be an atomic value that is an instance of an atomic type in the transitive membership of U, or a dynamic error may be raised as specified in [XQuery and XPath Functions and Operators 3.0].
If the transitive membership of the union type includes
xs:QName
, xs:NOTATION
, or a type derived
from either of these by restriction, then the namespace bindings in
the static context will be used to resolve any namespace prefix, in
the same way as when the target type is xs:QName
itself.
cast
is supported if the target type is a
non-primitive atomic type that is derived by restriction from the
input type. The input value must satisfy all the facets of the
target type (in the case of the pattern facet, this is checked by
generating a string representation of the input value, using the
rules for casting to xs:string
). The resulting value
is the same as the input value, but with a different dynamic type.
If a primitive type P1 can be cast into a primitive type P2, then any type derived by restriction from P1 can be cast into any type derived by restriction from P2, provided that the facets of the target type are satisfied. First the input value is cast to P1 using rule (b) above. Next, the value of type P1 is cast to the type P2, using rule (a) above. Finally, the value of type P2 is cast to the target type, using rule (d) above.
For any combination of input type and target type that is not in
the above list, a cast
expression raises a type error [err:XPTY0004].
If casting from the input type to the target type is supported
but nevertheless it is not possible to cast the input value into
the value space of the target type, a dynamic error is raised.
[err:FORG0001] This includes the case when any facet of the target
type is not satisfied. For example, the expression
"2003-02-31" cast as xs:date
would raise a dynamic error.
[92] | CastableExpr |
::= | CastExpr (
"castable" "as" SingleType
)? |
[163] | SingleType |
::= | AtomicOrUnionType
"?"? |
XQuery 3.0 provides an expression that tests whether a given
value is castable into a given target type. The target type must be
an atomic type that is in the in-scope schema types [err:XPST0051]. In addition, the target
type cannot be xs:NOTATION
or
xs:anyAtomicType
[err:XPST0080]. The optional occurrence indicator
"?
" denotes that an empty sequence is permitted.
The expression E castable as T
returns
true
if the result of evaluating E
can be
successfully cast into the target type T
by using a
cast
expression; otherwise it returns
false
. If evaluation of E
fails with a
dynamic error, the castable
expression as a whole
fails. The castable
expression can be used as a
predicate to avoid errors at
evaluation time. It can also be used to select an appropriate type
for processing of a given value, as illustrated in the following
example:
if ($x castable as hatsize) then $x cast as hatsize else if ($x castable as IQ) then $x cast as IQ else $x cast as xs:string
For every atomic type in the in-scope schema types (except
xs:NOTATION
and xs:anyAtomicType
, which
are not instantiable), a constructor function is implicitly
defined. In each case, the name of the constructor function is the
same as the name of its target type (including namespace). The
signature of the constructor function for type T is as
follows:
T($arg as xs:anyAtomicType?) as T?
[Definition: The constructor
function for a given type is used to convert instances of other
atomic types into the given type. The semantics of the constructor
function call T($arg)
are defined to be equivalent to
the expression (($arg) cast as T?)
.]
The following examples illustrate the use of constructor functions:
This example is equivalent to ("2000-01-01" cast as
xs:date?)
.
xs:date("2000-01-01")
This example is equivalent to (($floatvalue * 0.2E-5) cast
as xs:decimal?)
.
xs:decimal($floatvalue * 0.2E-5)
This example returns an xs:dayTimeDuration
value
equal to 21 days. It is equivalent to ("P21D" cast as
xs:dayTimeDuration?)
.
xs:dayTimeDuration("P21D")
If usa:zipcode
is a user-defined atomic type in the
in-scope schema
types, then the following expression is equivalent to the
expression ("12345" cast as usa:zipcode?)
.
usa:zipcode("12345")
Note:
An instance of an atomic type that is not in a namespace can be constructed in either of the following ways:
By using a cast
expression, if the default
element/type namespace is absentDM30.
(See 4.14
Default Namespace Declaration for how to undeclare the
default element/type
namespace).
17 cast as apple
By using a constructor function, if the default function namespace is absentDM30. (See 4.14 Default Namespace Declaration for how to undeclare the default function namespace).
apple(17)
[91] | TreatExpr |
::= | CastableExpr (
"treat" "as" SequenceType
)? |
XQuery 3.0 provides an expression called treat
that
can be used to modify the static type of its operand.
Like cast
, the treat
expression takes
two operands: an expression and a SequenceType. Unlike
cast
, however, treat
does not change the
dynamic type or
value of its operand. Instead, the purpose of treat
is
to ensure that an expression has an expected dynamic type at
evaluation time.
The semantics of expr1
treat
as
type1
are as follows:
During static analysis:
The static
type of the treat
expression is
type1
. This enables the expression to be
used as an argument of a function that requires a parameter of
type1
.
During expression evaluation:
If expr1
matches
type1
, using the rules for SequenceType matching, the
treat
expression returns the value of
expr1
; otherwise, it raises a dynamic error
[err:XPDY0050]. If
the value of expr1
is returned, its identity
is preserved. The treat
expression ensures that the
value of its expression operand conforms to the expected type at
run-time.
Example:
$myaddress treat as element(*, USAddress)
The static
type of $myaddress
may be element(*,
Address)
, a less specific type than element(*,
USAddress)
. However, at run-time, the value of
$myaddress
must match the type element(*,
USAddress)
using rules for SequenceType matching;
otherwise a dynamic error is raised [err:XPDY0050].
[99] | ValidateExpr |
::= | "validate" (ValidationMode | ("type"
TypeName))? "{" Expr "}" |
[100] | ValidationMode |
::= | "lax" | "strict" |
A validate
expression can be used to validate a
document node or an element node with respect to the in-scope schema
definitions, using the schema validation process defined in
[XML Schema 1.0] or [XML Schema 1.1]. If the operand of a
validate
expression does not evaluate to exactly one
document or element node, a type error is raised [err:XQTY0030]. In this specification, the
node that is the operand of a validate
expression is
called the operand node.
A validate
expression returns a new node with its
own identity and with no parent. The new node and its descendants
are given type annotation that are generated by
applying a validation process to the operand node. In some cases,
default values may also be generated by the validation process.
A validate
expression may optionally specify a
validation mode. The
default validation mode
(applicable when no type name is provided) is
strict
.
A validate
expression may optionally specify a
TypeName. This type name must
be found in the in-scope schema definitions; if it is not, a
static error is
raised [err:XQST0104]. If the type name is unprefixed,
it is interpreted as a name in the default namespace for elements
and types.
The result of a validate
expression is defined by
the following rules.
If the operand node is a document node, its children must consist of exactly one element node and zero or more comment and processing instruction nodes, in any order; otherwise, a dynamic error [err:XQDY0061] is raised.
The operand node is converted to an XML Information Set ([XML Infoset]) according to the "Infoset Mapping" rules defined in [XQuery and XPath Data Model (XDM) 3.0]. Note that this process discards any existing type annotations. Validity assessment is carried out on the root element information item of the resulting Infoset, using the in-scope schema definitions as the effective schema. The process of validation applies recursively to contained elements and attributes to the extent required by the effective schema.
If a type name is provided, schema-validity assessment is carried out according to the rules defined in [XML Schema 1.0] or [XML Schema 1.1] Part 1, section 3.3.4 "Element Declaration Validation Rules", "Validation Rule: Schema-Validity Assessment (Element)", clauses 1.2 and 2, using this type definition as the "processor-stipulated type definition" for validation.
When no type name is provided:
If validation mode is
strict
, then there must be a top-level element
declaration in the in-scope element declarations that matches the
root element information item in the Infoset, and schema-validity
assessment is carried out using that declaration in accordance with
[XML Schema 1.0] Part 1, section 5.2,
"Assessing Schema-Validity", item 2, or [XML
Schema 1.1] Part 1, section 5.2, "Assessing Schema-Validity",
"element-driven validation". If there is no such element
declaration, a dynamic error is raised [err:XQDY0084].
If validation mode is
lax
, then schema-validity assessment is carried out in
accordance with [XML Schema 1.0] Part 1,
section 5.2, "Assessing Schema-Validity", item 3, or [XML Schema 1.1] Part 1, section 5.2, "Assessing
Schema-Validity", "lax wildcard validation".
If validation mode is
lax
and the root element information item has neither
a top-level element declaration nor an xsi:type
attribute, [XML Schema 1.0] or [XML Schema 1.1] defines the recursive checking
of children and attributes as optional. During processing of an
XQuery validate
expression, this recursive checking is
required.
If the operand node is an element node, the validation rules named "Validation Root Valid (ID/IDREF)" is not applied. This means that document-level constraints relating to uniqueness and referential integrity are not enforced.
There is no check that the document contains unparsed entities
whose names match the values of nodes of type
xs:ENTITY
or xs:ENTITIES
.
Note:
Validity assessment is affected by the presence or absence of
xsi:type
attributes on the elements being validated,
and may generate new information items such as default
attributes.
The outcome of the validation expression depends on
the validity
property of the root element
information item in the PSVI that results from the validation
process.
If the validity
property of the root element
information item is valid
, or if validation mode is
lax
and the validity
property of the root
element information item is notKnown
, the PSVI is
converted back into an XDM instance as described in [XQuery and XPath Data Model (XDM) 3.0]
Section 3.3, "Construction from a PSVI". The resulting node (a new
node of the same kind as the operand node) is returned as the
result of the validate
expression.
Otherwise, a dynamic error is raised [err:XQDY0027].
Note:
The effect of these rules is as follows, where the validated element means either the operand node or (if the operand node is a document node) its element child.:
If validation mode is
strict
, the validated element must have a top-level
element declaration in the effective schema, and must conform to
this declaration.
If validation mode is
lax
, the validated element must conform to its
top-level element declaration if such a declaration exists in the
effective schema. If validation mode is
lax
and there is no top-level element declaration for
the element, and the element has an xsi:type
attribute, then the xsi:type
attribute must name a
top-level type definition in the effective schema, and the element
must conform to that type.
If a type name is specified in the validate expression, no attempt is made to locate an element declaration matching the name of the validated element; the element can have any name, and its content is validated against the named type.
Note:
During conversion of the PSVI into an XDM instance after validation,
any element information items whose validity property is
notKnown
are converted into element nodes with
type
annotation xs:anyType
, and any attribute
information items whose validity property is notKnown
are converted into attribute nodes with type annotation
xs:untypedAtomic
, as described in Section
3.3.1.1 Element and Attribute Node Types
DM30.
[Definition: An extension expression is an expression whose semantics are implementation-defined.] Typically a particular extension will be recognized by some implementations and not by others. The syntax is designed so that extension expressions can be successfully parsed by all implementations, and so that fallback behavior can be defined for implementations that do not recognize a particular extension.
[101] | ExtensionExpr |
::= | Pragma+ "{" Expr? "}" |
[102] | Pragma |
::= | "(#" S? EQName (S
PragmaContents)?
"#)" |
[103] | PragmaContents |
::= | (Char* - (Char* '#)'
Char*)) |
An extension expression consists of one or more pragmas,
followed by an expression enclosed in curly braces. [Definition: A
pragma is denoted by the delimiters (#
and
#)
, and consists of an identifying EQName followed by
implementation-defined content.]
The content of a pragma may consist of any string of characters
that does not contain the ending delimiter #)
. If the
EQName of a pragma is a lexical QName, it must resolve to a namespace URI
and local name, using the statically known namespaces
[err:XPST0081].
Note:
Since there is no default namespace for pragmas, a pragma's EQName must provide a URILiteral or a namespace prefix.
Each implementation recognizes an implementation-defined set of namespace URIs used to denote pragmas.
If the namespace URI of a pragma's expanded QName is not recognized by the implementation as a pragma namespace, then the pragma is ignored. If all the pragmas in an ExtensionExpr are ignored, then the value of the ExtensionExpr is the value of the expression enclosed in curly braces; if this expression is absent, then a static error is raised [err:XQST0079].
If an implementation recognizes the namespace of one or more pragmas in an ExtensionExpr, then the value of the ExtensionExpr, including its error behavior, is implementation-defined. For example, an implementation that recognizes the namespace of a pragma's expanded QName, but does not recognize the local part of the name, might choose either to raise an error or to ignore the pragma.
It is a static error [err:XQST0013] if an implementation recognizes a pragma but determines that its content is invalid.
If an implementation recognizes a pragma, it must report any static errors in the following expression even if it will not evaluate that expression (however, static type errors are raised only if the Static Typing Feature is in effect.)
Note:
The following examples illustrate three ways in which extension expressions might be used.
A pragma can be used to furnish a hint for how to evaluate the following expression, without actually changing the result. For example:
declare namespace exq = "http://example.org/XQueryImplementation"; (# exq:use-index #) { $bib/book/author[name='Berners-Lee'] }
An implementation that recognizes the exq:use-index
pragma might use an index to evaluate the expression that follows.
An implementation that does not recognize this pragma would
evaluate the expression in its normal way.
A pragma might be used to modify the semantics of the following
expression in ways that would not (in the absence of the pragma) be
conformant with this specification. For example, a pragma might be
used to permit comparison of xs:duration
values using
implementation-defined semantics (this would normally be an error).
Such changes to the language semantics must be scoped to the
expression contained within the curly braces following the
pragma.
A pragma might contain syntactic constructs that are evaluated in place of the following expression. In this case, the following expression itself (if it is present) provides a fallback for use by implementations that do not recognize the pragma. For example:
declare namespace exq = "http://example.org/XQueryImplementation"; for $x in (# exq:distinct //city by @country #) { //city[not(@country = preceding::city/@country)] } return f:show-city($x)
Here an implementation that recognizes the pragma will return
the result of evaluating the proprietary syntax exq:distinct
//city by @country
, while an implementation that does not
recognize the pragma will instead return the result of the
expression //city[not(@country =
preceding::city/@country)]
. If no fallback expression is
required, or if none is feasible, then the expression between the
curly braces may be omitted, in which case implementations that do
not recognize the pragma will raise a static error.
[1] | Module |
::= | VersionDecl?
(LibraryModule | MainModule) |
[3] | MainModule |
::= | Prolog QueryBody |
[4] | LibraryModule |
::= | ModuleDecl
Prolog |
[6] | Prolog |
::= | ((DefaultNamespaceDecl |
Setter | NamespaceDecl | Import) Separator)* ((ContextItemDecl | AnnotatedDecl | OptionDecl) Separator)* |
[8] | Setter |
::= | BoundarySpaceDecl | DefaultCollationDecl |
BaseURIDecl | ConstructionDecl | OrderingModeDecl | EmptyOrderDecl | CopyNamespacesDecl |
DecimalFormatDecl |
[20] | Import |
::= | SchemaImport |
ModuleImport |
[7] | Separator |
::= | ";" |
[38] | QueryBody |
::= | Expr |
A query can be assembled from one or more fragments called modules. [Definition: A module is a fragment of XQuery code that conforms to the Module grammar and can independently undergo the static analysis phase described in 2.2.3 Expression Processing. Each module is either a main module or a library module.]
[Definition: A main module consists of a Prolog followed by a Query Body.] A query has exactly one main module. In a main module, the Query Body can be evaluated, and its value is the result of the query.
[Definition: A module that does not contain a Query Body is called a library module. A library module consists of a module declaration followed by a Prolog.] A library module cannot be evaluated directly; instead, it provides function and variable declarations that can be imported into other modules.
The XQuery syntax does not allow a module to contain both a module declaration and a Query Body.
[Definition: A Prolog is a series of declarations and imports that define the processing environment for the module that contains the Prolog.] Each declaration or import is followed by a semicolon. A Prolog is organized into two parts.
The first part of the Prolog consists of setters, imports, namespace declarations, and default namespace declarations. [Definition: Setters are declarations that set the value of some property that affects query processing, such as construction mode, ordering mode, or default collation.] Namespace declarations and default namespace declarations affect the interpretation of lexical QNames within the query. Imports are used to import definitions from schemas and modules. [Definition: The target namespace of a module is the namespace of the objects (such as elements or functions) that it defines. ]
The second part of the Prolog consists of declarations of variables, functions, and options. These declarations appear at the end of the Prolog because they may be affected by declarations and imports in the first part of the Prolog.
[Definition: The Query Body, if present, consists of an expression that defines the result of the query.] Evaluation of expressions is described in 3 Expressions. A module can be evaluated only if it has a Query Body.
[2] | VersionDecl |
::= | "xquery" (("encoding" StringLiteral) | ("version"
StringLiteral ("encoding"
StringLiteral)?))
Separator |
[Definition: A version declaration can identify the applicable XQuery syntax and semantics for a module, as well as its encoding.] The version number "1.0" indicates a requirement that the module must be processed by an XQuery 1.0 processor; the version number "3.0" indicates a requirement that the module must be processed by an XQuery 3.0 processor. If the version declaration is not present or the version is not included in the declaration, an XQuery 3.0 processor assumes a version of "3.0". If an XQuery 3.0 processor processes a module labeled with a version of "1.0", it must either raise a static error [err:XQST0031], or attempt to process the module with an XQuery 1.0 processor. If any version number other than 3.0 or 1.0 is encountered, a static error [err:XQST0031] is raised.
[Definition: If present, a version
declaration may optionally include an encoding declaration.
The value of the string literal following the keyword
encoding
is an encoding name, and must conform to the
definition of EncName
specified in [XML
1.0] [err:XQST0087]. The purpose of an encoding
declaration is to allow the writer of a query to provide a string
that indicates how the query is encoded, such as
"UTF-8
", "UTF-16
", or
"US-ASCII
".] Since the encoding of a query may change
as the query moves from one environment to another, there can be no
guarantee that the encoding declaration is correct.
The handling of an encoding declaration is implementation-dependent. If an implementation has a priori knowledge of the encoding of a query, it may use this knowledge and disregard the encoding declaration. The semantics of a query are not affected by the presence or absence of an encoding declaration.
If a version declaration is present, no Comment may occur before the end of the version declaration. If such a Comment is present, the result is implementation-dependent.
Note:
The effect of a Comment before the end of a version declaration is implementation-dependent because it may suppress query processing by interfering with detection of the encoding declaration.
The following examples illustrate version declarations:
xquery version "1.0";
xquery version "1.0" encoding "utf-8";
[5] | ModuleDecl |
::= | "module" "namespace" NCName "=" URILiteral Separator |
[Definition: A module
declaration serves to identify a module as a library module. A module declaration
begins with the keyword module
and contains a
namespace prefix and a URILiteral.] The URILiteral must be
of nonzero length [err:XQST0088]. The URILiteral identifies the
target
namespace of the library module, which is the namespace for all
variables and functions exported by the library module. The name of
every variable and function declared in a library module must have
a namespace URI that is the same as the target namespace of the
module; otherwise a static error is raised [err:XQST0048]. In the
statically known namespaces of the
library module, the namespace prefix specified in the module
declaration is bound to the module's target namespace.
The namespace prefix specified in a module declaration must not
be xml
or xmlns
[err:XQST0070], and must not be the same as
any namespace prefix bound in the same module by a schema import, by a
namespace declaration, or by a
module import
with a different target namespace [err:XQST0033].
Any module may import one or more library modules by means of a module import that specifies the target namespace of the library modules to be imported. When a module imports one or more library modules, the variables and functions declared in the imported modules are added to the static context and (where applicable) to the dynamic context of the importing module.
The following is an example of a module declaration:
module namespace gis = "http://example.org/gis-functions";
[9] | BoundarySpaceDecl |
::= | "declare" "boundary-space" ("preserve" |
"strip") |
[Definition: A
boundary-space declaration sets the boundary-space policy in the
static
context, overriding any implementation-defined default.
Boundary-space policy controls whether boundary
whitespace is preserved by element constructors during
processing of the query.] If boundary-space policy is
preserve
, boundary whitespace is preserved. If
boundary-space policy is strip
, boundary whitespace is
stripped (deleted). A further discussion of whitespace in
constructed elements can be found in 3.8.1.4 Boundary Whitespace.
The following example illustrates a boundary-space declaration:
declare boundary-space preserve;
If a Prolog contains more than one boundary-space declaration, a static error is raised [err:XQST0068].
[10] | DefaultCollationDecl |
::= | "declare" "default" "collation" URILiteral |
[Definition: A default
collation declaration sets the value of the default collation
in the static
context, overriding any implementation-defined default.] The
default collation is the collation that is used by functions and
operators that require a collation if no other collation is
specified. For example, the gt
operator on strings is
defined by a call to the fn:compare
function, which
takes an optional collation parameter. Since the gt
operator does not specify a collation, the fn:compare
function implements gt
by using the default
collation.
If neither the implementation nor the Prolog specifies a default
collation, the Unicode codepoint collation
(http://www.w3.org/2005/xpath-functions/collation/codepoint
)
is used.
The following example illustrates a default collation declaration:
declare default collation "http://example.org/languages/Icelandic";
If a default collation declaration specifies a collation by a relative URI, that relative URI is resolved to an absolute URI using the Static Base URI. If a Prolog contains more than one default collation declaration, or the value specified by a default collation declaration (after resolution of a relative URI, if necessary) is not present in statically known collations, a static error is raised [err:XQST0038].
[11] | BaseURIDecl |
::= | "declare" "base-uri" URILiteral |
[Definition: A base URI declaration specifies the Static Base URI property. The Static Base URI property is used when resolving relative URIs during static analysis. ] For example, the Static Base URI property is used when resolving relative URIs for module import.
The following is an example of a base URI declaration:
declare base-uri "http://example.org";
If a Prolog contains more than one base URI declaration, a static error is raised [err:XQST0032].
In the terminology of [RFC3986] Section
5.1, the URILiteral of the base URI declaration is considered to be
a "base URI embedded in content". If no base URI declaration is
present, Static Base URI property is
established according to the principles outlined in [RFC3986] Section 5.1—that is, it defaults first to
the base URI of the encapsulating entity, then to the URI used to
retrieve the entity, and finally to an implementation-defined
default. If the URILiteral in the base URI declaration is a
relative URI, then it is made absolute by resolving it with respect
to this same hierarchy. For example, if the URILiteral in the base
URI declaration is ../data/
, and the query is
contained in a file whose URI is
file:///C:/temp/queries/query.xq
, then the
Static
Base URI property is
file:///C:/temp/data/
.
It is not intrinsically an error if this process fails to establish an absolute base URI; however, the Static Base URI property is then undefined [err:XPST0001]. When the Static Base URI property is undefined, any attempt to use its value to resolve a relative URI reference will result in an error [err:XPST0001].
[12] | ConstructionDecl |
::= | "declare" "construction" ("strip" |
"preserve") |
[Definition: A construction
declaration sets the construction mode in the static context,
overriding any implementation-defined default.] The construction
mode governs the behavior of element and document node
constructors. If construction mode is preserve
, the
type of a constructed element node is xs:anyType
, and
all attribute and element nodes copied during node construction
retain their original types. If construction mode is
strip
, the type of a constructed element node is
xs:untyped
; all element nodes copied during node
construction receive the type xs:untyped
, and all
attribute nodes copied during node construction receive the type
xs:untypedAtomic
.
The following example illustrates a construction declaration:
declare construction strip;
If a Prolog specifies more than one construction declaration, a static error is raised [err:XQST0067].
[13] | OrderingModeDecl |
::= | "declare" "ordering" ("ordered" |
"unordered") |
[Definition: An ordering
mode declaration sets the ordering mode in the static context,
overriding any implementation-defined default.] This ordering mode
applies to all expressions in a module (including both the Prolog and the Query Body, if any), unless overridden by an
ordered
or unordered
expression.
The following example illustrates an ordering mode declaration:
declare ordering unordered;
If a Prolog contains more than one ordering mode declaration, a static error is raised [err:XQST0065].
[14] | EmptyOrderDecl |
::= | "declare" "default" "order" "empty" ("greatest" |
"least") |
[Definition: An empty order
declaration sets the default order for empty sequences in
the static
context, overriding any implementation-defined default. This
declaration controls the processing of empty sequences and
NaN
values as ordering keys in an order
by
clause in a FLWOR expression.] An individual order
by
clause may override the default order for empty sequences
by specifying empty greatest
or empty
least
.
The following example illustrates an empty order declaration:
declare default order empty least;
If a Prolog contains more than one empty order declaration, a static error is raised [err:XQST0069].
Note:
It is important to distinguish an empty order
declaration from an ordering mode declaration. An
empty order declaration applies only
when an order by
clause is present, and specifies how
empty sequences are treated by the order by
clause
(unless overridden). An ordering mode declaration, on the
other hand, applies only in the absence of an order by
clause.
[15] | CopyNamespacesDecl |
::= | "declare" "copy-namespaces" PreserveMode "," InheritMode |
[16] | PreserveMode |
::= | "preserve" | "no-preserve" |
[17] | InheritMode |
::= | "inherit" | "no-inherit" |
[Definition: A copy-namespaces declaration sets the value of copy-namespaces mode in the static context, overriding any implementation-defined default. Copy-namespaces mode controls the namespace bindings that are assigned when an existing element node is copied by an element constructor or document constructor.] Handling of namespace bindings by element constructors is described in 3.8.1 Direct Element Constructors.
The following example illustrates a copy-namespaces declaration:
declare copy-namespaces preserve, no-inherit;
If a Prolog contains more than one copy-namespaces declaration, a static error is raised [err:XQST0055].
[18] | DecimalFormatDecl |
::= | "declare" (("decimal-format" EQName) | ("default" "decimal-format"))
(DFPropertyName "="
StringLiteral)* |
[19] | DFPropertyName |
::= | "decimal-separator" | "grouping-separator" | "infinity" |
"minus-sign" | "NaN" | "percent" | "per-mille" | "zero-digit" |
"digit" | "pattern-separator" |
[Definition: A
decimal-format declaration adds a decimal format to the
statically known decimal formats,
which define the properties used to format numbers using the
fn:format-number()
function], as described in [XQuery and XPath Functions and Operators
3.0]. The mapping between these properties and the equivalent
fn:format-number()
properties is discussed in
statically known decimal formats,
which also specifies the defaults for each value. If a format
declares no properties, default values are used for all
properties.
It is a static error for a query prolog to contain two decimal format declarations with the same name, or to contain two default decimal format declarations [err:XQST0111]. It is a static error for a decimal format declaration to define the same property more than once [err:XQST0114]. It is a static error for a decimal-format declaration to specify a value that is not valid for a given property, as described in statically known decimal formats [err:XQST0097]. It is a static error if, for any named or unnamed decimal format, the properties representing characters used in a picture string do not have distinct values [err:XQST0098]. The following properties represent characters used in a picture string: decimal-separator-sign, grouping-separator, percent-sign, per-mille-sign, zero-digit, digit-sign, and pattern-separator-sign .
[21] | SchemaImport |
::= | "import" "schema" SchemaPrefix? URILiteral ("at" URILiteral ("," URILiteral)*)? |
[22] | SchemaPrefix |
::= | ("namespace" NCName
"=") | ("default" "element" "namespace") |
[Definition: A schema import imports the element declarations, attribute declarations, and type definitions from a schema into the in-scope schema definitions. For each user-defined atomic type in the schema, schema import also adds a corresponding constructor function. ] The schema to be imported is identified by its target namespace. The schema import may bind a namespace prefix to the target namespace of the imported schema, or may declare that target namespace to be the default element/type namespace. The schema import may also provide optional hints for locating the schema.
The namespace prefix specified in a schema import must not be
xml
or xmlns
[err:XQST0070], and must not be the same as
any namespace prefix bound in the same module by another schema
import, a module
import, a namespace declaration, or a
module
declaration [err:XQST0033].
The first URILiteral in a
schema import specifies the target namespace of the schema to be
imported. The URILiterals that follow the at
keyword
are optional location hints, and can be interpreted or disregarded
in an implementation-dependent way. Multiple location hints might
be used to indicate more than one possible place to look for the
schema or multiple physical resources to be assembled to form the
schema.
A schema import that specifies a zero-length string as target namespace is considered to import a schema that has no target namespace. Such a schema import must not bind a namespace prefix [err:XQST0057], but it may set the default element/type namespace to a zero-length string (representing "no namespace"), thus enabling the definitions in the imported namespace to be referenced. If the default element/type namespace is not set to "no namespace", there is no way to reference the definitions in an imported schema that has no target namespace.
It is a static
error [err:XQST0058] if more than one schema import in
the same Prolog specifies
the same target namespace. It is a static error [err:XQST0059] if the implementation is not able
to process a schema import by finding a valid schema with the
specified target namespace. It is a static error [err:XQST0035] if multiple imported schemas, or
multiple physical resources within one schema, contain definitions
for the same name in the same symbol space (for example, two
definitions for the same element name, even if the definitions are
consistent). However, it is not an error to import the schema with
target namespace http://www.w3.org/2001/XMLSchema
(predeclared prefix xs
), even though the built-in
types defined in this schema are implicitly included in the
in-scope schema
types.
It is a static error [err:XQST0012] if the set of definitions contained in all schemas imported by a Prolog do not satisfy the conditions for schema validity specified in Sections 3 and 5 of [XML Schema 1.0] or [XML Schema 1.1] Part 1--i.e., each definition must be valid, complete, and unique.
The following example imports a schema, specifying both its
target namespace and its location, and binding the prefix
soap
to the target namespace:
import schema namespace soap="http://www.w3.org/2003/05/soap-envelope" at "http://www.w3.org/2003/05/soap-envelope/";
The following example imports a schema by specifying only its target namespace, and makes it the default element/type namespace:
import schema default element namespace "http://example.org/abc";
The following example imports a schema that has no target namespace, providing a location hint, and sets the default element/type namespace to "no namespace" so that the definitions in the imported schema can be referenced:
import schema default element namespace "" at "http://example.org/xyz.xsd";
The following example imports a schema that has no target namespace and sets the default element/type namespace to "no namespace". Since no location hint is provided, it is up to the implementation to find the schema to be imported.
import schema default element namespace "";
[23] | ModuleImport |
::= | "import" "module" ("namespace" NCName "=")? URILiteral ("at" URILiteral ("," URILiteral)*)? |
[Definition: A module import imports the public variable declarations and public function declarations from one or more library modules into the function signatures and in-scope variables of the importing module.] Each module import names a target namespace and imports an implementation-defined set of modules that share this target namespace. The module import may bind a namespace prefix to the target namespace, and it may provide optional hints for locating the modules to be imported.
The following example illustrates a module import:
import module namespace gis="http://example.org/gis-functions";
If a query imports the same module via multiple paths, only one instance of the module is imported. Because only one instance of a module is imported, there is only one instance of each global variable declared in a module.
A module may import its own target namespace (this is interpreted as importing an implementation-defined set of other modules that share its target namespace.)
The namespace prefix specified in a module import must not be
xml
or xmlns
[err:XQST0070], and must not be the same as
any namespace prefix bound in the same module by another module
import, a schema
import, a namespace declaration, or a
module
declaration with a different target namespace [err:XQST0033].
The first URILiteral in a
module import must be of nonzero length [err:XQST0088], and specifies the target
namespace of the modules to be imported. The URILiterals that
follow the at
keyword are optional location hints, and
can be interpreted or disregarded in an implementation-defined way.
It is a static
error [err:XQST0047] if more than one module import in
a Prolog specifies the same
target namespace. It is a static error [err:XQST0059] if the implementation is not able
to process a module import by finding a valid module definition
with the specified target namespace. It is a static error if the
expanded
QName of a variable declared in an imported module is equal (as
defined by the eq
operator) to the expanded QName of a
variable declared in the importing module or in another imported
module (even if the declarations are consistent) [err:XQST0049].
Each module has its own static context. A module import imports only functions and variable declarations; it does not import other objects from the imported modules, such as in-scope schema definitions or statically known namespaces. Module imports are not transitive—that is, importing a module provides access only to function and variable declarations contained directly in the imported module. For example, if module A imports module B, and module B imports module C, module A does not have access to the functions and variables declared in module C.
A module import does not import schema definitions from the imported module. In the following query, the type geometry:triangle is not defined, even if it is known in the imported module, so the variable declaration raises an error [err:XPST0051]:
(: Error - geometry:triangle is not defined :) import module namespace geo = "http://example.org/geo-functions"; declare variable $t as geometry:triangle := geo:make-triangle(); $t
Without the type declaration for the variable, the variable declaration succeeds:
import module namespace geo = "http://example.org/geo-functions"; declare variable $t := geometry:make-triangle(); $t
Importing the schema that defines the type of the variable, the variable declaration succeeds:
import schema namespace geo = "http://example.org/geo-schema-declarations"; import module namespace geo = "http://example.org/geo-functions"; declare variable $t as geometry:triangle := geo:make-triangle(); $t
Module URIs should be treated in the same way as other namespace URIs.
To maximize interoperability, query authors should use a string that is a valid absolute IRI.
Implementions must accept any string of Unicode characters. Module URIs are compared using the Unicode codepoint collation rather than any concept of semantic equivalence.
Implementations may provide mechanisms allowing the module URI to be used as input to a process that delivers the module as a resource, for example a catalog, module repository, or URI resolver. For interoperability, such mechanisms should not prevent the user from choosing an arbitrary URI for naming a module.
Similarly, implementations may perform syntactic transformations on the module URI to obtain the names of related resources, for example to implement a convention relating the name or location of compiled code to the module URI; but again, such mechanisms should not prevent the user from choosing an arbitrary module URI.
As with other namespace URIs, it is common practice to use module URIs whose scheme is "http" and whose authority part uses a DNS domain name under the control of the user.
The specifications allow, and some users might consider it good practice, for the module URI of a function library to be the same as the namespace URI of the XML vocabulary manipulated by the functions in that library.
Several different modules with the same Module URI can be used in the same query. The names of public global variables and public functions must be unique within the query as a whole: that is, if two modules with the same module URI are used in the same query, the names of their global variables and functions must not overlap.
If one module contains an "import module" declaration for the module URI M, then all public global variables and public functions declared in participating modules whose module URI is M must be accessible in the importing module, regardless whether the participation of the imported module was directly due to this "import module" declaration.
The term "location URIs" refers to the URIs in the "at" clause of an "import module" declaration.
Products should (by default or at user option) take account of all the location URIs in an "import module" declaration, treating each location URI as a reference to a module with the specified module URI. Location URIs should be made absolute with respect to the static base URI of the module containing the "import module" declaration where they appear. The mapping from location URIs to module source code or compiled code MAY be done in any way convenient to the implementation. If possible given the product's architecture, security requirements, etc, the product should allow this to fetch the source code of the module to use the standard web mechanisms for dereferencing URIs in standard schemes such as the "http" URI scheme.
When the same absolutized location URI is used more than once, either in the same "import module" declaration or in different "import module" declarations within the same query, a single copy of the resource containing the module is loaded. When different absolutized location URIs are used, each results in a single module being loaded, unless the implementation is able to determine that the different URIs are references to the same resource. No error due to duplicate variable or functions names should arise from the same module being imported more than once, so long as the absolute location URI is the same in each case.
Implementations must report a static error if a location URI cannot be resolved after all available recovery strategies have been exhausted.
[24] | NamespaceDecl |
::= | "declare" "namespace" NCName "=" URILiteral |
[Definition: A namespace declaration declares a namespace prefix and associates it with a namespace URI, adding the (prefix, URI) pair to the set of statically known namespaces.] The namespace declaration is in scope throughout the query in which it is declared, unless it is overridden by a namespace declaration attribute in a direct element constructor.
If the URILiteral part of a namespace declaration is a
zero-length string, any existing namespace binding for the given
prefix is removed from the statically known namespaces. This
feature provides a way to remove predeclared namespace prefixes
such as local
.
The following query illustrates a namespace declaration:
declare namespace foo = "http://example.org"; <foo:bar> Lentils </foo:bar>
In the query result, the newly created node is in the namespace
associated with the namespace URI
http://example.org
.
The namespace prefix specified in a namespace declaration must
not be xml
or xmlns
[err:XQST0070]. The
namespace URI specified in a namespace declaration must not be
http://www.w3.org/XML/1998/namespace
or
http://www.w3.org/2000/xmlns/
[err:XQST0070]. The namespace prefix
specified in a namespace declaration must not be the same as any
namespace prefix bound in the same module by a module import,
schema
import, module declaration, or another namespace
declaration [err:XQST0033].
It is a static error [err:XPST0081] if an expression contains a lexical QName with a namespace prefix that is not in the statically known namespaces.
XQuery has several predeclared namespace prefixes that are
present in the statically known namespaces before each
query is processed. These prefixes may be used without an explicit
declaration. They may be overridden by namespace
declarations in a Prolog or by namespace declaration attributes on
constructed elements (however, the prefix xml
must not
be redeclared, and no other prefix may be bound to the namespace
URI associated with the prefix xml
[err:XQST0070]). The
predeclared namespace prefixes are as follows:
xml = http://www.w3.org/XML/1998/namespace
xs = http://www.w3.org/2001/XMLSchema
xsi = http://www.w3.org/2001/XMLSchema-instance
fn = http://www.w3.org/2005/xpath-functions
local =
http://www.w3.org/2005/xquery-local-functions
(see 4.18 Function Declaration.)
Additional predeclared namespace prefixes may be added to the statically known namespaces by an implementation.
When element or attribute names are compared, they are considered identical if the local parts and namespace URIs match on a codepoint basis. Namespace prefixes need not be identical for two names to match, as illustrated by the following example:
declare namespace xx = "http://example.org"; let $i := <foo:bar xmlns:foo = "http://example.org"> <foo:bing> Lentils </foo:bing> </foo:bar> return $i/xx:bing
Although the namespace prefixes xx
and
foo
differ, both are bound to the namespace URI
"http://example.org"
. Since xx:bing
and
foo:bing
have the same local name and the same
namespace URI, they match. The output of the above query is as
follows.
<foo:bing xmlns:foo = "http://example.org"> Lentils </foo:bing>
[25] | DefaultNamespaceDecl |
::= | "declare" "default" ("element" | "function") "namespace"
URILiteral |
Default namespace declarations can be used in a Prolog to facilitate the use of unprefixed QNames. The following kinds of default namespace declarations are supported:
A default element/type namespace declaration declares a namespace URI that is associated with unprefixed names of elements and types. This declaration is recorded as the default element/type namespace in the static context. A Prolog may contain at most one default element/type namespace declaration [err:XQST0066]. If the URILiteral in a default element/type namespace declaration is a zero-length string, the default element/type namespace is undeclared (set to absentDM30), and unprefixed names of elements and types are considered to be in no namespace. The following example illustrates the declaration of a default namespace for elements and types:
declare default element namespace "http://example.org/names";
A default element/type namespace declaration may be overridden by a namespace declaration attribute in a direct element constructor.
If no default element/type namespace declaration is present, unprefixed element and type names are in no namespace (however, an implementation may define a different default as specified in C.1 Static Context Components.)
A default function namespace declaration declares a namespace URI that is associated with unprefixed function names in function calls and function declarations. This declaration is recorded as the default function namespace in the static context. A Prolog may contain at most one default function namespace declaration [err:XQST0066]. If the StringLiteral in a default function namespace declaration is a zero-length string, the default function namespace is undeclared (set to absentDM30). In that case, any functions that are associated with a namespace can be called only by using an explicit namespace prefix.
If no default function namespace declaration is present, the
default function namespace is the namespace of XPath/XQuery
functions, http://www.w3.org/2005/xpath-functions
(however, an implementation may define a different default as
specified in C.1
Static Context Components.)
The following example illustrates the declaration of a default function namespace:
declare default function namespace "http://www.w3.org/2005/xpath-functions/math";
The effect of declaring a default function namespace is that all functions in the default function namespace, including implicitly-declared constructor functions, can be invoked without specifying a namespace prefix. When a function call uses a function name with no prefix, the local name of the function must match a function (including implicitly-declared constructor functions) in the default function namespace [err:XPST0017].
Note:
Only constructor functions can be in no namespace.
Unprefixed attribute names and variable names are in no namespace.
[26] | AnnotatedDecl |
::= | "declare" Annotation* (VarDecl | FunctionDecl) |
[27] | Annotation |
::= | "%" EQName ("("
Literal ("," Literal)* ")")? |
XQuery uses annotations to declare properties associated with
functions and variables. For instance, a function may be declared
%public
or %private
. The
semantics associated with these properties are described in
4.18 Function Declaration.
Annotations are (QName, value)
pairs. If the EQName
of the annotation is a lexical QName, the prefix of the QName is resolved
using the statically known namespaces; if no prefix is present, the
name is in the default function namespace. The XQuery family
of languages define annotations in the fn
namespace.
Assuming this the default element namespace is fn
, the
annotations %private
and %fn:private
both
have the same annotation name.
Implementations MAY define further annotations, whose behaviour is
implementation-defined. For instance, if the eg
prefix
is bound to a namespace associated with a particular
implementation, it could define an annotation like
eg:sequential
. Implementations MUST NOT define annotations in the following
reserved namespaces; it is an error for users to create
annotations in the following reserved namespaces [err:XQST0045]:
http://www.w3.org/XML/1998/namespace
http://www.w3.org/2001/XMLSchema
http://www.w3.org/2001/XMLSchema-instance
http://www.w3.org/2005/xpath-functions
http://www.w3.org/2005/xpath-functions/math
An annotation can provide values explicitly using a
parenthesized list of literals.
For instance, the annotation
%java:method("java.lang.Math.sin")
sets the value of
the java:method
annotation to the string value
java.lang.Math.sin
.
[26] | AnnotatedDecl |
::= | "declare" Annotation* (VarDecl | FunctionDecl) |
[27] | Annotation |
::= | "%" EQName ("("
Literal ("," Literal)* ")")? |
[28] | VarDecl |
::= | "variable" "$" VarName TypeDeclaration? ((":="
VarValue) | ("external" (":="
VarDefaultValue)?)) |
[125] | VarName |
::= | EQName |
[164] | TypeDeclaration |
::= | "as" SequenceType |
[29] | VarValue |
::= | ExprSingle |
[30] | VarDefaultValue |
::= | ExprSingle |
A variable declaration adds the static type of a variable to the in-scope variables, and may also add a value for the variable to the variable values.
Note:
A variable declaration always refers to a declaration of a variable in a Prolog. The binding of a variable to a value in a query expression, such as a FLWOR expression, is known as a variable binding, and does not make the variable visible to an importing module.
During static analysis, a variable declaration causes a pair
(expanded QName N, type T)
to be added to the
in-scope variables. The expanded QName
N is the VarName
. If N is equal (as defined by the eq
operator) to the expanded QName of another variable in in-scope
variables, a static
error is raised [err:XQST0049].
All variable names declared in a library module must (when
expanded) be in the target namespace of the library module
[err:XQST0048]. A
variable declaration may use function annotations to specify that
the variable is %private
or %public
(which is the default). [Definition: A
private variable is a variable with a %private
annotation. A private variable is hidden from module import, which
can not import it into the in-scope variables of another module.]
[Definition: A public variable is a
variable with a %public
annotation. A public variable
is accessible to module import, which can import it into the
in-scope variables of another module.
It is a static
error [err:XQST0116] if a variable declaration's's
annotations contain more than one annotation named
%private
or %public
.]
Variable names that have no namespace prefix are in no namespace. Variable declarations that have no namespace prefix may appear only in a main module.
Here are some examples of variable declarations:
The following declaration specifies both the type and the value
of a variable. This declaration causes the type
xs:integer
to be associated with variable
$x
in the static context, and the value
7
to be associated with variable $x
in
the dynamic
context.
declare variable $x as xs:integer := 7;
The following declaration specifies a value but not a type. The
static type of
the variable is inferred from the static type of its value. In this
case, the variable $x
has a static type of
xs:decimal
, inferred from its value which is 7.5.
declare variable $x := 7.5;
The following declaration specifies a type but not a value. The
keyword external
indicates that the value of the
variable will be provided by the external environment. At
evaluation time, if the variable $x
in the dynamic context
does not have a value of type xs:integer
, a type error is raised.
declare variable $x as xs:integer external;
The following declaration specifies neither a type nor a value.
It simply declares that the query depends on the existence of a
variable named $x
, whose type and value will be
provided by the external environment. During query analysis, the
type of $x
is considered to be item()*
.
During query evaluation, the dynamic context must include a type and a
value for $x
, and its value must be compatible with
its type.
declare variable $x external;
The following declaration, which might appear in a library module, declares a variable whose name includes a namespace prefix:
declare variable $sasl:username as xs:string := "jonathan@example.com";
This is an example of an external variable declaration that
provides a VarDefaultValue
:
declare variable $x as xs:integer external := 47;
The syntax for variable declarations allows annotations, but XQuery 3.0 does not define annotations that apply to variable declarations. An implementation can provide annotations it needs. For instance, an implemenation that supports volatile external variables might allow them to be declared using an annotation:
declare %eg:volatile variable $time as xs:time external;
The type of the declared variable is as follows:
If TypeDeclaration
is present, then the
SequenceType
in the TypeDeclaration
;
otherwise
If the Static Typing Feature is in effect and
VarValue
is present, then the static type inferred
from static analysis of the expression VarValue
;
Note:
Type inference might not be computable until after the check for circular dependencies, described below, is complete.
Otherwise, item()*
.
[Definition: If a variable declaration
includes an expression (VarValue
or
VarDefaultValue
), the expression is called an
initializing expression. The static context for an
initializing expression includes all functions, variables, and
namespaces that are declared or imported anywhere in the Prolog,
other than the variable being declared.]
[Definition: An expression
E
depends on a variable V
if any
of the following is true:
|
]
If the initializer of a variable V
depends
on V
, a static error is raised [err:XQST0054].
During query evaluation, each variable declaration causes a pair
(expanded QName N, value V)
to be added to the
variable
values. The expanded QName N is the VarName
. The
value V is as follows:
If VarValue
is specified, then V is the result of
evaluating VarValue
as described below.
If external
is specified, then:
if a value is provided for the variable by the external environment, then V is that value. The means by which typed values of external variables are provided by the external environment is implementation-defined.
if no value is provided for the variable by the external
environment, and VarDefaultValue
is specified, then V
is the result of evaluating VarDefaultValue
as
described below.
If no value is provided for the variable by the external
environment, and VarDefaultValue
is not specified,
then a dynamic
error is raised [err:XPDY0002].
It is implementation-dependent whether this error is raised if the evaluation of the query does not reference the value of the variable.
In all cases the value V must match the type T according to the rules for SequenceType matching; otherwise a type error is raised [err:XPTY0004].
If VarValue
or VarDefaultValue
is
evaluated, the dynamic context for the evaluation is as
follows:
The variable values contain the values of all variables present in the static context.
Note:
A cyclic dependency between variables is a static error, so it is always possible to evaluate all the variables that V depends on before evaluating V.)
The function implementations contains the implementation of each function present in the static context
All other properties of the dynamic context, including the
context item, position, and size, are the same as for the
evaluation of the QueryBody
of the main module.
[31] | ContextItemDecl |
::= | "declare" "context" "item" ("as" ItemType)? ((":=" VarValue) | ("external" (":=" VarDefaultValue)?)) |
A context item declaration allows a query to specify the static type, value, or default value for the initial context item.
In a library module, a context item declaration specifies only the static type. Specifying a VarValue or VarDefaultValue for a context item declaration in a library module is a static error [err:XQST0113].
In every module that does not contain a context item declaration, the effect is as if the declaration
declare context item as item() external;
appeared in that module.
During static analysis, the context item declaration has the
effect of setting the context item static type in the static
context. The context item static type is set to
ItemType
if specified, or to item()
otherwise.
If a module contains more than one context item declaration, a static error is raised [err:XQST0099].
The static context for an initializing expression includes all functions, variables, and namespaces that are declared or imported anywhere in the Prolog.
[Definition: An expression
E
depends on the context item if any of the
following is true:
|
]
If the initializer of the context item depends on the context item, a static error is raised [err:XQST0107].
During query evaluation, the context item in the dynamic context
for the evaluation of the QueryBody
in the main
module, and for the initializing expression of every variable
declaration in every module, is set as follows:
If VarValue
is specified, then the result of
evaluating VarValue
as described below.
If external
is specified, then:
if a value is provided for the context item by the external environment, then that value.
The means by which an external value is provided by the external environment is implementation-defined.
if no value is provided for the context item by the external
environment, and VarDefaultValue
is specified, then
the result of evaluating VarDefaultValue
as described
below.
if no value is provided for the context item by the external
environment, and VarDefaultValue
is not specified,
then the context item is undefined, and a dynamic error is raised
[err:XPDY0002] if
the context item is referenced in the query.
In all cases where the context item has a value, that value must
match the type T
according to the rules for
SequenceType matching; otherwise a type error is raised [err:XPTY0004]. If more than
one module contains a context item declaration, the context item
must match the type declared in each one.
If VarValue
or VarDefaultValue
is
evaluated, the dynamic context for the evaluation is as
follows:
The variable values contains the values of all variables present in the static context
The context item, position, and size are undefined
Function implementations includes an implementation of each function present in the static context of the expression
All other properties of the dynamic context are the same as for
the evaluation of the QueryBody
of the main
module.
Here are some examples of context item declarations.
Declare the type of the context item:
declare namespace env="http://www.w3.org/2003/05/soap-envelope"; declare context item as element(env:Envelope) external;
Declare a default context item, which is a system log in a default location. If the system log is in a different location, it can be specified in the external environment:
declare context item as element(sys:log) external := doc("/var/xlogs/sysevent.xml");
Declare the context item to always point to a particular collection:
declare context item := collection("docs");
In addition to the built-in functions described in [XQuery and XPath Functions and Operators 3.0], XQuery allows users to declare functions of their own. A function declaration specifies the name of the function, the names and datatypes of the parameters, and the datatype of the result. All datatypes are specified using the syntax described in 2.5 Types. A function declaration causes the declared function to be added to the function signatures of the module in which it appears.
[26] | AnnotatedDecl |
::= | "declare" Annotation* (VarDecl | FunctionDecl) |
[27] | Annotation |
::= | "%" EQName ("("
Literal ("," Literal)* ")")? |
[32] | FunctionDecl |
::= | "function" EQName "("
ParamList? ")" ("as" SequenceType)? (FunctionBody |
"external") |
[33] | ParamList |
::= | Param ("," Param)* |
[34] | Param |
::= | "$" EQName TypeDeclaration? |
[35] | FunctionBody |
::= | EnclosedExpr |
[164] | TypeDeclaration |
::= | "as" SequenceType |
A function declaration specifies whether a function is user-defined or external.
[Definition: User defined functions are functions that contain a function body, which provides the implementation of the function as an XQuery expression.] The static context for a function body includes all functions, variables, and namespaces that are declared or imported anywhere in the Prolog, including the function being declared.
[Definition: External functions are
functions that are implemented outside the query environment.] For
example, an XQuery implementation might provide a set of external
functions in addition to the core function library described in
[XQuery and XPath Functions and
Operators 3.0]. External functions are identified by the
keyword external
. The purpose of a function
declaration for an external function is to declare the datatypes of
the function parameters and result, for use in type checking of the
query that contains or imports the function declaration.
A function declaration may use function annotations to specify
that a function is %private
or %public
(which is the default). [Definition: A
private function is a function with a %private
annotation. A private function is hidden from module import, which
can not import it into the function signatures of another module.
] [Definition: A public function is a
function with a %public
annotation. A public function
is accessible to module import, which can import it into the
function signatures of another module.
] It is a static
error [err:XQST0106] if a function's annotations
contain more than one annotation named %private
or
%public
.
An XQuery implementation may provide a facility whereby external
functions can be implemented using a host programming language, but
it is not required to do so. If such a facility is provided, the
protocols by which parameters are passed to an external function,
and the result of the function is returned to the invoking query,
are implementation-defined. An XQuery
implementation may augment the type system of [XQuery and XPath Data Model (XDM) 3.0]
with additional types that are designed to facilitate exchange of
data with host programming languages, or it may provide mechanisms
for the user to define such types. For example, a type might be
provided that encapsulates an object returned by an external
function, such as an SQL database connection. These additional
types, if defined, are considered to be derived by restriction from
xs:anyAtomicType
.
An implementation can define annotations, in its own namespace, to support functionality beyond the scope of this specification. For instance, an implementation that supports external Java functions might use an annotation to associate a Java function with an XQuery external function:
declare %java:method("java.lang.StrictMath.copySign") function smath:copySign($magnitude, $sign) external;
Every declared function must be in a namespace; that is, every declared function name must (when expanded) have a non-null namespace URI [err:XQST0060]. If the function name in a function declaration has no namespace prefix, it is considered to be in the default function namespace. Every function name declared in a library module must (when expanded) be in the target namespace of the library module [err:XQST0048]. It is a static error [err:XQST0045] if the function name in a function declaration (when expanded) is in any of the following namespaces:
http://www.w3.org/XML/1998/namespace
http://www.w3.org/2001/XMLSchema
http://www.w3.org/2001/XMLSchema-instance
http://www.w3.org/2005/xpath-functions
http://www.w3.org/2005/xpath-functions/math
In order to allow main modules to declare functions for local
use within the module without defining a new namespace, XQuery
predefines the namespace prefix local
to the namespace
http://www.w3.org/2005/xquery-local-functions
. It is
suggested (but not required) that this namespace be used for
defining local functions.
If a function parameter is declared using a name but no type,
its default type is item()*
. If the result type is
omitted from a function declaration, its default result type is
item()*
.
The parameters of a function declaration are considered to be variables whose scope is the function body. It is an static error [err:XQST0039] for a function declaration to have more than one parameter with the same name. The type of a function parameter can be any type that can be expressed as a sequence type.
The following example illustrates the declaration and use of a
local function that accepts a sequence of employee
elements, summarizes them by department, and returns a sequence of
dept
elements.
Using a function, prepare a summary of employees that are located in Denver.
declare function local:summary($emps as element(employee)*) as element(dept)* { for $d in fn:distinct-values($emps/deptno) let $e := $emps[deptno = $d] return <dept> <deptno>{$d}</deptno> <headcount> {fn:count($e)} </headcount> <payroll> {fn:sum($e/salary)} </payroll> </dept> }; local:summary(fn:doc("acme_corp.xml")//employee[location = "Denver"])
Rules for converting function arguments to their declared parameter types, and for converting the result of a function to its declared result type, are described in 3.1.5 Function Calls.
A function declaration may be recursive—that is, it may
reference itself. Mutually recursive functions, whose bodies
reference each other, are also allowed. The following example
declares a recursive function that computes the maximum depth of a
node hierarchy, and calls the function to find the maximum depth of
a particular document. The function local:depth
calls
the built-in functions empty
and max
,
which are in the default function namespace.
Find the maximum depth of the document named
partlist.xml
.
declare function local:depth($e as node()) as xs:integer { (: A node with no children has depth 1 :) (: Otherwise, add 1 to max depth of children :) if (fn:empty($e/*)) then 1 else fn:max(for $c in $e/* return local:depth($c)) + 1 }; local:depth(fn:doc("partlist.xml"))
[Definition: An expression
E
depends on a function if any of the following
is true:
|
]
[Definition: An option declaration declares an option that affects the behavior of a particular implementation. Each option consists of an identifying EQName and a StringLiteral.]
[37] | OptionDecl |
::= | "declare" "option" EQName StringLiteral |
Typically, a particular option will be recognized by some implementations and not by others. The syntax is designed so that option declarations can be successfully parsed by all implementations.
If the EQName of an option is a lexical QName, it must resolve to a namespace URI and local name, using the statically known namespaces [err:XPST0081].
Note:
There is no default namespace for options.
Each implementation recognizes an implementation-defined set of namespace URIs used to denote option declarations.
If the namespace part of the expanded QName is not a namespace recognized by the implementation as one used to denote option declarations, then the option declaration is ignored.
Otherwise, the effect of the option declaration, including its error behavior, is implementation-defined. For example, if the local part of the QName is not recognized, or if the StringLiteral does not conform to the rules defined by the implementation for the particular option declaration, the implementation may choose whether to report an error, ignore the option declaration, or take some other action.
Implementations may impose rules on where particular option declarations may appear relative to variable declarations and function declarations, and the interpretation of an option declaration may depend on its position.
An option declaration must not be used to change the syntax accepted by the processor, or to suppress the detection of static errors. However, it may be used without restriction to modify the semantics of the query. The scope of the option declaration is implementation-defined—for example, an option declaration might apply to the whole query, to the current module, or to the immediately following function declaration.
The following examples illustrate several possible uses for option declarations:
This option declaration might be used to specify how comments in
source documents returned by the fn:doc()
function
should be handled:
declare option exq:strip-comments "true";
This option declaration might be used to associate a namespace used in function names with a Java class:
declare namespace smath = "http://example.org/MathLibrary"; declare option exq:java-class "smath = java.lang.StrictMath";
Note:
The XQuery Working Group has not yet determined conformance criteria for XQuery 3.0; in particular, we have not decided which of the new features of XQuery 3.0 are optional. This section currently contains the conformance criteria for XQuery 1.0, with two modifications: (1) support for all axes is now required, (2) conformance criteria for syntax extensions are given.
This section defines the conformance criteria for an XQuery processor. In this section, the following terms are used to indicate the requirement levels defined in [RFC 2119]. [Definition: MUST means that the item is an absolute requirement of the specification.] [Definition: MUST NOT means that the item is an absolute prohibition of the specification.] [Definition: MAY means that an item is truly optional.] [Definition: SHOULD means that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.]
An XQuery processor that claims to conform to this specification MUST include a claim of Minimal Conformance as defined in 5.1 Minimal Conformance. In addition to a claim of Minimal Conformance, it MAY claim conformance to one or more optional features defined in 5.2 Optional Features.
Minimal Conformance to this specification MUST include all of the following items:
Support for everything specified in this document except those features specified in 5.2 Optional Features to be optional. If an implementation does not provide a given optional feature, it MUST implement any requirements specified in 5.2 Optional Features for implementations that do not provide that feature.
A definition of every item specified to be implementation-defined, unless that item is part of an optional feature that is not supported by the implementation. A list of implementation-defined items can be found in D Implementation-Defined Items.
Note:
Implementations are not required to define items specified to be implementation-dependent.
Support for [XQuery and XPath Data Model (XDM) 3.0], as specified in 5.3 Data Model Conformance.
Support for all functions defined in [XQuery and XPath Functions and Operators 3.0].
[Definition: The Schema Import Feature permits the query Prolog to contain a schema import.]
If an XQuery implementation does not support the Schema Import Feature, it MUST raise a static error [err:XQST0009] if it encounters a schema import.
Note:
If an implementation does not support the Schema Import Feature, the in-scope schema types consist only of built-in and implementation-defined schema type definitions, as described in C.1 Static Context Components.
[Definition: The Schema
Validation Feature permits a query to contain a
validate
expression (see 3.16 Validate Expressions.)]
If an XQuery implementation does not support the Schema
Validation Feature, it MUST raise
a static error [err:XQST0075] if it encounters a
validate
expression.
[Definition: The Static Typing Feature requires implementations to report all type errors during the static analysis phase.]
If an implementation supports the Static Typing Feature, then it MUST report an error during static analysis whenever the inferred static type of an expression is not subsumed by the required type for the context in which it appears.
If an implementation does not support the Static Typing Feature, then it MAY report type errors during the static analysis phase only in cases where the inferred static type and the required type have an empty intersection (that is, where evaluation of the expression is guaranteed to fail). It MAY defer some or all type checking until the dynamic evaluation phase.
[Definition: A conforming XQuery implementation that supports the Module Feature allows a query Prolog to contain a Module Import and allows library modules to be created.]
A conforming implementation that does not support the Module Feature MUST raise a static error [err:XQST0016] if it encounters a module declaration or a module import. Since a module declaration is required in a library module, the Module Feature is required in order to create a library module.
Note:
In the absence of the Module Feature, each query consists of a single main module.
[Definition: A conforming XQuery implementation that supports the Serialization Feature MUST provide means for serializing the result of a query, as specified in 2.2.4 Serialization.]
A conforming XQuery implementation that supports the Serialization Feature MUST conform to 2.2.4 Serialization. The means by which serialization is invoked is implementation-defined.
If an error is raised during the serialization process as specified in [XSLT and XQuery Serialization 3.0], a conforming XQuery implementation MUST report the error to the calling environment.
Note:
Not all implementations need to serialize. For instance, an implementation might provide results via an XML API instead of producing a textual representation.
All XQuery implementations process data represented in the data model as specified in [XQuery and XPath Data Model (XDM) 3.0]. The data model specification relies on languages such as XQuery to specify conformance criteria for the data model in their respective environments, and suggests that the following issues should be considered:
Support for normative construction from an infoset. A conforming implementation MAY choose to claim conformance to Section 3.2 Construction from an Infoset DM30, which defines a normative way to construct an XDM instance from an XML document that is merely well-formed or is governed by a DTD.
Support for normative construction from a PSVI. A conforming implementation MAY choose to claim conformance to Section 3.3 Construction from a PSVI DM30, which defines a normative way to construct an XDM instance from an XML document that is governed by a W3C XML Schema.
Support for XML 1.0 and XML 1.1. The [XQuery and XPath Data Model (XDM) 3.0] supports either [XML 1.0] or [XML 1.1]. In XQuery, the choice of which XML version to support is implementation-defined.
At the time of writing there is no published version of XML
Schema that references the XML 1.1 specifications. This means that
datatypes such as xs:NCName
and xs:ID
are
constrained by the XML 1.0 rules. It is recommended that an XQuery
1.0 processor should implement the rules defined by later versions
of XML Schema as they become available.
Note:
For suggestions on processing XML 1.1 documents, see [XML 1.1 and Schema 1.0].
Ranges of data values. In XQuery, the following limits are implementation-defined:
For the xs:decimal
type, the maximum number of
decimal digits (totalDigits
facet) (must be at least
18).
For the types xs:date
, xs:time
,
xs:dateTime
, xs:gYear
, and
xs:gYearMonth
: the maximum value of the year component
and the maximum number of fractional second digits (must be at
least 3).
For the xs:duration type
: the maximum absolute
values of the years, months, days, hours, minutes, and seconds
components.
For the xs:yearMonthDuration
type: the maximum
absolute value, expressed as an integer number of months.
For the xs:dayTimeDuration
type: the maximum
absolute value, expressed as a decimal number of seconds.
For the types xs:string
, xs:hexBinary
,
xs:base64Binary
, xs:QName
,
xs:anyURI
, xs:NOTATION
, and types derived
from them: limitations (if any) imposed by the implementation on
lengths of values.
The limits listed above need not be fixed, but may depend on
environmental factors such as system resources. For example, the
length of a value of type xs:string
may be limited by
available memory.
Any syntactic extensions to XQuery are implementation-defined. The effect of syntactic extensions, including their error behavior, is implementation-defined. Syntactic extensions may be used without restriction to modify the semantics of a XQuery expression.
The grammar of XQuery 3.0 uses the same simple Extended Backus-Naur Form (EBNF) notation as [XML 1.0] with the following minor differences.
All named symbols have a name that begins with an uppercase letter.
It adds a notation for referring to productions in external specs.
Comments or extra-grammatical constraints on grammar productions are between '/*' and '*/' symbols.
A 'xgc:' prefix is an extra-grammatical constraint, the details of which are explained in A.1.2 Extra-grammatical Constraints
A 'ws:' prefix explains the whitespace rules for the production, the details of which are explained in A.2.4 Whitespace Rules
A 'gn:' prefix means a 'Grammar Note', and is meant as a clarification for parsing rules, and is explained in A.1.3 Grammar Notes. These notes are not normative.
The terminal symbols for this grammar include the quoted strings used in the production rules below, and the terminal symbols defined in section A.2.1 Terminal Symbols.
The EBNF notation is described in more detail in A.1.1 Notation.
To increase readability, the EBNF in the main body of this document omits some of these notational features. This appendix is the normative version of the EBNF.
The following definitions will be helpful in defining precisely this exposition.
[Definition: Each rule in the grammar defines one symbol, using the following format:
symbol ::= expression
]
[Definition: A terminal is a symbol or string or pattern that can appear in the right-hand side of a rule, but never appears on the left hand side in the main grammar, although it may appear on the left-hand side of a rule in the grammar for terminals.] The following constructs are used to match strings of one or more characters in a terminal:
matches any Char with a value in the range(s) indicated (inclusive).
matches any Char with a value among the characters enumerated.
matches any Char with a value not among the characters given.
matches the sequence of characters that appear inside the double quotes.
matches the sequence of characters that appear inside the single quotes.
matches any string matched by the production defined in the external specification as per the provided reference.
Patterns (including the above constructs) can be combined with grammatical operators to form more complex patterns, matching more complex sets of character strings. In the examples that follow, A and B represent (sub-)patterns.
A
is treated as a unit and may be combined as
described in this list.
matches A
or nothing; optional A
.
matches A
followed by B
. This operator
has higher precedence than alternation; thus A B | C D
is identical to (A B) | (C D)
.
matches A
or B
but not both.
matches any string that matches A
but does not
match B
.
matches one or more occurrences of A
. Concatenation
has higher precedence than alternation; thus A+ | B+
is identical to (A+) | (B+)
.
matches zero or more occurrences of A
.
Concatenation has higher precedence than alternation; thus A*
| B*
is identical to (A*) | (B*)
This section contains constraints on the EBNF productions, which are required to parse syntactically valid sentences. The notes below are referenced from the right side of the production, with the notation: /* xgc: <id> */.
Constraint: leading-lone-slash
A single slash may appear either as a complete path expression
or as the first part of a path expression in which it is followed
by a RelativePathExpr.
In some cases, the next token after the slash is insufficient to
allow a parser to distinguish these two possibilities: the
*
token and keywords like union
could be
either an operator or a NameTest , and
the <
token could be either an operator or the
start of a DirectConstructor .
For example, without lookahead the first part of the expression
/ * 5
is easily taken to be a complete expression,
/ *
, which has a very different interpretation (the
child nodes of /
).
Therefore to reduce the need for lookahead, if the token immediately following a slash can form the start of a RelativePathExpr, then the slash must be the beginning of a PathExpr, not the entirety of it.
A single slash may be used as the left-hand argument of an
operator by parenthesizing it: (/) * 5
. The expression
5 * /
, on the other hand, is syntactically valid
without parentheses.
An implementation's choice to support the [XML
1.0] and [XML Names], or [XML 1.1] and [XML Names
1.1] lexical specification determines the external document
from which to obtain the definition for this production. The EBNF
only has references to the 1.0 versions. In some cases, the XML 1.0
and XML 1.1 definitions may be exactly the same. Also please note
that these external productions follow the whitespace rules of
their respective specifications, and not the rules of this
specification, in particular A.2.4.1 Default Whitespace
Handling. Thus prefix : localname
is not a
syntactically valid lexical QName for purposes of this specification,
just as it is not permitted in a XML document. Also, comments are
not permissible on either side of the colon. Also extra-grammatical
constraints such as well-formedness constraints must be taken into
account.
Constraint: reserved-function-names
Unprefixed function names spelled the same way as language
keywords could make the language harder to recognize. For instance,
if(foo)
could be taken either as a FunctionCall or as the beginning
of an IfExpr. Therefore, an
unprefixed function name must not be any of the names in A.3 Reserved Function Names.
A function named "if" can be called by binding its namespace to a prefix and using the prefixed form: "library:if(foo)" instead of "if(foo)".
Constraint: occurrence-indicators
As written, the grammar in A XQuery 3.0 Grammar is ambiguous for some forms using the '+' and '*' Kleene operators. The ambiguity is resolved as follows: these operators are tightly bound to the SequenceType expression, and have higher precedence than other uses of these symbols. Any occurrence of '+' and '*', as well as '?', following a sequence type is assumed to be an occurrence indicator, which binds to the last ItemType in the SequenceType.
Thus, 4 treat as item() + - 5
must be interpreted
as (4 treat as item()+) - 5
, taking the '+' as an
OccurrenceIndicator and the '-' as a subtraction operator. To force
the interpretation of "+" as an addition operator (and the
corresponding interpretation of the "-" as a unary minus),
parentheses may be used: the form (4 treat as item()) +
-5
surrounds the SequenceType expression with
parentheses and leads to the desired interpretation.
function () as xs:string *
is interpreted as
function () as (xs:string *)
, not as (function
() as xs:string) *
. Parentheses can be used as shown to
force the latter interpretation.
This rule has as a consequence that certain forms which would otherwise be syntactically valid and unambiguous are not recognized: in "4 treat as item() + 5", the "+" is taken as an OccurrenceIndicator, and not as an operator, which means this is not a syntactically valid expression.
This section contains general notes on the EBNF productions, which may be helpful in understanding how to interpret and implement the EBNF. These notes are not normative. The notes below are referenced from the right side of the production, with the notation: /* gn: <id> */.
Note:
Look-ahead is required to distinguish FunctionCall from a EQName or
keyword followed by a Pragma or Comment. For example: address (:
this may be empty :)
may be mistaken for a call to a
function named "address" unless this lookahead is employed. Another
example is for (: whom the bell :) $tolls in 3 return
$tolls
, where the keyword "for" must not be mistaken for a
function name.
Comments are allowed everywhere that ignorable whitespace is allowed, and the Comment symbol does not explicitly appear on the right-hand side of the grammar (except in its own production). See A.2.4.1 Default Whitespace Handling. Note that comments are not allowed in direct constructor content, though they are allowed in nested EnclosedExprs.
A comment can contain nested comments, as long as all "(:" and ":)" patterns are balanced, no matter where they occur within the outer comment.
Note:
Lexical analysis may typically handle nested comments by incrementing a counter for each "(:" pattern, and decrementing the counter for each ":)" pattern. The comment does not terminate until the counter is back to zero.
Some illustrative examples:
(: commenting out a (: comment :) may be confusing, but
often helpful :)
is a syntactically valid Comment, since
balanced nesting of comments is allowed.
"this is just a string :)"
is a syntactically valid
expression. However, (: "this is just a string :)" :)
will cause a syntax error. Likewise, "this is another string
(:"
is a syntactically valid expression, but (: "this
is another string (:" :)
will cause a syntax error. It is a
limitation of nested comments that literal content can cause
unbalanced nesting of comments.
for (: set up loop :) $i in $x return $i
is
syntactically valid, ignoring the comment.
5 instance (: strange place for a comment :) of
xs:integer
is also syntactically valid.
<eg (: an example:)>{$i//title}</eg>
is
not syntactically valid.
<eg> (: an example:) </eg>
is
syntactically valid, but the characters that look like a comment
are in fact literal element content.
The terminal symbols assumed by the grammar above are described in this section.
Quoted strings appearing in production rules are terminal symbols.
Other terminal symbols are defined in A.2.1 Terminal Symbols.
It is implementation-defined whether the lexical rules of [XML 1.0] and [XML Names] are followed, or alternatively, the lexical rules of [XML 1.1] and [XML Names 1.1] are followed. Implementations that support the full [XML 1.1] character set SHOULD, for purposes of interoperability, provide a mode that follows only the [XML 1.0] and [XML Names] lexical rules.
When tokenizing, the longest possible match that is valid in the current context is used.
All keywords are case sensitive. Keywords are not reserved—that is, any lexical QName may duplicate a keyword except as noted in A.3 Reserved Function Names.
The following symbols are used only in the definition of terminal symbols; they are not terminal symbols in the grammar of A.1 EBNF.
[211] | Digits |
::= | [0-9]+ |
[212] | CommentContents |
::= | (Char+ - (Char* ('(:' |
':)') Char*)) |
XQuery 3.0 expressions consist of terminal symbols and symbol separators.
Terminal symbols that are not used exclusively in /* ws: explicit */ productions are of two kinds: delimiting and non-delimiting.
[Definition: The delimiting terminal symbols are: S, "!=", StringLiteral, "#", "#)", "$", "%", "(", "(#", ")", "*", "+", (comma), "-", "-->", (dot), "..", "/", "//", "/>", (colon), "::", ":=", (semi-colon), "<", "<!--", "<![CDATA[", "</", "<<", "<=", "<?", "=", ">", ">=", ">>", "?", "?>", "@", "[", "]", "]]>", "{", "|", "}" ]
[Definition: The non-delimiting terminal symbols are: IntegerLiteral, NCName, DecimalLiteral, DoubleLiteral, QName, "NaN", "allowing", "ancestor", "ancestor-or-self", "and", "as", "ascending", "at", "attribute", "base-uri", "boundary-space", "by", "case", "cast", "castable", "catch", "child", "collation", "comment", "construction", "context", "copy-namespaces", "count", "decimal-format", "decimal-separator", "declare", "default", "descendant", "descendant-or-self", "descending", "digit", "div", "document", "document-node", "element", "else", "empty", "empty-sequence", "encoding", "end", "eq", "every", "except", "external", "following", "following-sibling", "for", "function", "ge", "greatest", "group", "grouping-separator", "gt", "idiv", "if", "import", "in", "infinity", "inherit", "instance", "intersect", "is", "item", "lax", "le", "least", "let", "lt", "minus-sign", "mod", "module", "namespace", "namespace-node", "ne", "next", "no-inherit", "no-preserve", "node", "of", "only", "option", "or", "order", "ordered", "ordering", "parent", "pattern-separator", "per-mille", "percent", "preceding", "preceding-sibling", "preserve", "previous", "processing-instruction", "return", "satisfies", "schema", "schema-attribute", "schema-element", "self", "sliding", "some", "stable", "start", "strict", "strip", "switch", "text", "then", "to", "treat", "try", "tumbling", "type", "typeswitch", "union", "unordered", "validate", "variable", "version", "when", "where", "window", "xquery", "zero-digit" ]
[Definition: Whitespace and Comments function as symbol separators. For the most part, they are not mentioned in the grammar, and may occur between any two terminal symbols mentioned in the grammar, except where that is forbidden by the /* ws: explicit */ annotation in the EBNF, or by the /* xgc: xml-version */ annotation.]
It is customary to separate consecutive terminal symbols by whitespace and Comments, but this is required only when otherwise two non-delimiting symbols would be adjacent to each other. There are two exceptions to this, that of "." and "-", which do require a symbol separator if they follow a QName or NCName. Also, "." requires a separator if it precedes or follows a numeric literal.
The XQuery 3.0 processor must behave as if it normalized all line breaks on input, before parsing. The normalization should be done according to the choice to support either [XML 1.0] or [XML 1.1] lexical processing.
For [XML 1.0] processing, all of the following must be translated to a single #xA character:
the two-character sequence #xD #xA
any #xD character that is not immediately followed by #xA.
For [XML 1.1] processing, all of the following must be translated to a single #xA character:
the two-character sequence #xD #xA
the two-character sequence #xD #x85
the single character #x85
the single character #x2028
any #xD character that is not immediately followed by #xA or #x85.
The characters #x85 and #x2028 cannot be reliably recognized and translated until the VersionDecl declaration (if present) has been read.
[Definition: A whitespace character is any of the characters defined by [http://www.w3.org/TR/REC-xml/#NT-S].]
[Definition: Ignorable whitespace consists of any whitespace characters that may occur between terminals, unless these characters occur in the context of a production marked with a ws:explicit annotation, in which case they can occur only where explicitly specified (see A.2.4.2 Explicit Whitespace Handling).] Ignorable whitespace characters are not significant to the semantics of an expression. Whitespace is allowed before the first terminal and after the last terminal of a module. Whitespace is allowed between any two terminals. Comments may also act as "whitespace" to prevent two adjacent terminals from being recognized as one. Some illustrative examples are as follows:
foo- foo
results in a syntax error. "foo-" would be
recognized as a QName.
foo -foo
is syntactically equivalent to foo -
foo
, two QNames separated by a subtraction operator.
foo(: This is a comment :)- foo
is syntactically
equivalent to foo - foo
. This is because the comment
prevents the two adjacent terminals from being recognized as
one.
foo-foo
is syntactically equivalent to single
QName. This is because "-" is a valid character in a QName. When
used as an operator after the characters of a name, the "-" must be
separated from the name, e.g. by using whitespace or
parentheses.
10div 3
results in a syntax error.
10 div3
also results in a syntax error.
10div3
also results in a syntax error.
Explicit whitespace notation is specified with the EBNF productions, when it is different from the default rules, using the notation shown below. This notation is not inherited. In other words, if an EBNF rule is marked as /* ws: explicit */, the notation does not automatically apply to all the 'child' EBNF productions of that rule.
/* ws: explicit */ means that the EBNF notation explicitly
notates, with S
or otherwise, where whitespace characters are
allowed. In productions with the /* ws: explicit */ annotation,
A.2.4.1 Default Whitespace
Handling does not apply. Comments are also not allowed in these
productions.
For example, whitespace is not freely allowed by the direct constructor productions, but is specified explicitly in the grammar, in order to be more consistent with XML.
The following names are not allowed as function names in an unprefixed form because expression syntax takes precedence.
attribute
comment
document-node
element
empty-sequence
function
if
item
namespace-node
node
processing-instruction
schema-attribute
schema-element
switch
text
typeswitch
The grammar in A.1 EBNF normatively defines built-in precedence among the operators of XQuery. These operators are summarized here to make clear the order of their precedence from lowest to highest. The associativity column indicates the order in which operators of equal precedence in an expression are applied.
# | Operator | Associativity |
---|---|---|
1 | , (comma) | either |
2 | FLWOR, some, every, switch, typeswitch, try, if | NA |
3 | or | either |
4 | and | either |
5 | eq, ne, lt, le, gt, ge, =, !=, <, <=, >, >=, is, <<, >> | NA |
6 | to | NA |
7 | +, - (binary) | left-to-right |
8 | *, div, idiv, mod | left-to-right |
9 | union, | | either |
10 | intersect, except | left-to-right |
11 | instance of | NA |
12 | treat as | NA |
13 | castable as | NA |
14 | cast as | NA |
15 | -, + (unary) | right-to-left |
16 | /, // | left-to-right |
17 | [ ] | left-to-right |
In the "Associativity" column, "either" indicates that all the
operators at that level have the associative property (i.e.,
(A op B) op C
is equivalent to A op (B op
C)
), so their associativity is inconsequential. "NA" (not
applicable) indicates that the EBNF does not allow an expression
that directly contains multiple operators from that precedence
level, so the question of their associativity does not arise.
Note:
Parentheses can be used to override the operator precedence in the usual way. Square brackets in an expression such as A[B] serve two roles: they act as an operator causing B to be evaluated once for each item in the value of A, and they act as parentheses enclosing the expression B.
Curly braces in an expression such as validate{E} or ordered{E} perform a similar bracketing role to the parentheses in a function call, but with the difference in most cases that E is an Expr rather than ExprSingle, meaning that it can use the comma operator.
[Definition: Under certain circumstances, an
atomic value can be promoted from one type to another. Type
promotion is used in evaluating function calls (see 3.1.5 Function Calls), order by
clauses (see 3.9.8 Order By Clause), and
operators that accept numeric or string operands (see B.2 Operator Mapping).] The following type
promotions are permitted:
Numeric type promotion:
A value of type xs:float
(or any type derived by
restriction from xs:float
) can be promoted to the type
xs:double
. The result is the xs:double
value that is the same as the original value.
A value of type xs:decimal
(or any type derived by
restriction from xs:decimal
) can be promoted to either
of the types xs:float
or xs:double
. The
result of this promotion is created by casting the original value
to the required type. This kind of promotion may cause loss of
precision.
URI type promotion: A value of type xs:anyURI
(or
any type derived by restriction from xs:anyURI
) can be
promoted to the type xs:string
. The result of this
promotion is created by casting the original value to the type
xs:string
.
Note:
Since xs:anyURI
values can be promoted to
xs:string
, functions and operators that compare
strings using the default collation also compare
xs:anyURI
values using the default collation.
This ensures that orderings that include strings,
xs:anyURI
values, or any combination of the two types
are consistent and well-defined.
Note that type promotion is different from subtype substitution. For example:
A function that expects a parameter $p
of type
xs:float
can be invoked with a value of type
xs:decimal
. This is an example of type promotion. The
value is actually converted to the expected type. Within the body
of the function, $p instance of xs:decimal
returns
false
.
A function that expects a parameter $p
of type
xs:decimal
can be invoked with a value of type
xs:integer
. This is an example of subtype
substitution. The value retains its original type. Within the
body of the function, $p instance of xs:integer
returns true
.
The operator mapping tables in this section list the combinations of types for which the various operators of XQuery 3.0 are defined. [Definition: For each operator and valid combination of operand types, the operator mapping tables specify a result type and an operator function that implements the semantics of the operator for the given types.] The definitions of the operator functions are given in [XQuery and XPath Functions and Operators 3.0]. The result of an operator may be the raising of an error by its operator function, as defined in [XQuery and XPath Functions and Operators 3.0]. In some cases, the operator function does not implement the full semantics of a given operator. For the definition of each operator (including its behavior for empty sequences or sequences of length greater than one), see the descriptive material in the main part of this document.
The and
and or
operators are defined
directly in the main body of this document, and do not occur in the
operator mapping tables.
If an operator in the operator mapping tables expects an operand
of type ET, that operator can be applied to an operand of
type AT if type AT can be converted to type
ET by a combination of type promotion and subtype
substitution. For example, a table entry indicates that the
gt
operator may be applied to two xs:date
operands, returning xs:boolean
. Therefore, the
gt
operator may also be applied to two (possibly
different) subtypes of xs:date
, also returning
xs:boolean
.
[Definition: When referring to a type, the term
numeric denotes the types xs:integer
,
xs:decimal
, xs:float
, and
xs:double
.] An operator whose operands and result are
designated as numeric
might be thought of as representing four operators, one for each of
the numeric types. For example, the numeric +
operator
might be thought of as representing the following four
operators:
Operator | First operand type | Second operand type | Result type |
+ |
xs:integer |
xs:integer |
xs:integer |
+ |
xs:decimal |
xs:decimal |
xs:decimal |
+ |
xs:float |
xs:float |
xs:float |
+ |
xs:double |
xs:double |
xs:double |
A numeric operator may be validly applied to an operand of type
AT if type AT can be converted to any of the four
numeric types by a combination of type promotion and subtype
substitution. If the result type of an operator is listed as
numeric, it means "the first type in the ordered list
(xs:integer, xs:decimal, xs:float, xs:double)
into
which all operands can be converted by subtype
substitution and type promotion." As an example, suppose
that the type hatsize
is derived from
xs:integer
and the type shoesize
is
derived from xs:float
. Then if the +
operator is invoked with operands of type hatsize
and
shoesize
, it returns a result of type
xs:float
. Similarly, if +
is invoked with
two operands of type hatsize
it returns a result of
type xs:integer
.
[Definition: In the operator mapping tables, the
term Gregorian refers to the types
xs:gYearMonth
, xs:gYear
,
xs:gMonthDay
, xs:gDay
, and
xs:gMonth
.] For binary operators that accept two
Gregorian-type operands, both operands must have the same type (for
example, if one operand is of type xs:gDay
, the other
operand must be of type xs:gDay
.)
Operator | Type(A) | Type(B) | Function | Result type |
---|---|---|---|---|
A + B | numeric | numeric | op:numeric-add(A, B) | numeric |
A + B | xs:date | xs:yearMonthDuration | op:add-yearMonthDuration-to-date(A, B) | xs:date |
A + B | xs:yearMonthDuration | xs:date | op:add-yearMonthDuration-to-date(B, A) | xs:date |
A + B | xs:date | xs:dayTimeDuration | op:add-dayTimeDuration-to-date(A, B) | xs:date |
A + B | xs:dayTimeDuration | xs:date | op:add-dayTimeDuration-to-date(B, A) | xs:date |
A + B | xs:time | xs:dayTimeDuration | op:add-dayTimeDuration-to-time(A, B) | xs:time |
A + B | xs:dayTimeDuration | xs:time | op:add-dayTimeDuration-to-time(B, A) | xs:time |
A + B | xs:dateTime | xs:yearMonthDuration | op:add-yearMonthDuration-to-dateTime(A, B) | xs:dateTime |
A + B | xs:yearMonthDuration | xs:dateTime | op:add-yearMonthDuration-to-dateTime(B, A) | xs:dateTime |
A + B | xs:dateTime | xs:dayTimeDuration | op:add-dayTimeDuration-to-dateTime(A, B) | xs:dateTime |
A + B | xs:dayTimeDuration | xs:dateTime | op:add-dayTimeDuration-to-dateTime(B, A) | xs:dateTime |
A + B | xs:yearMonthDuration | xs:yearMonthDuration | op:add-yearMonthDurations(A, B) | xs:yearMonthDuration |
A + B | xs:dayTimeDuration | xs:dayTimeDuration | op:add-dayTimeDurations(A, B) | xs:dayTimeDuration |
A - B | numeric | numeric | op:numeric-subtract(A, B) | numeric |
A - B | xs:date | xs:date | op:subtract-dates(A, B) | xs:dayTimeDuration |
A - B | xs:date | xs:yearMonthDuration | op:subtract-yearMonthDuration-from-date(A, B) | xs:date |
A - B | xs:date | xs:dayTimeDuration | op:subtract-dayTimeDuration-from-date(A, B) | xs:date |
A - B | xs:time | xs:time | op:subtract-times(A, B) | xs:dayTimeDuration |
A - B | xs:time | xs:dayTimeDuration | op:subtract-dayTimeDuration-from-time(A, B) | xs:time |
A - B | xs:dateTime | xs:dateTime | op:subtract-dateTimes(A, B) | xs:dayTimeDuration |
A - B | xs:dateTime | xs:yearMonthDuration | op:subtract-yearMonthDuration-from-dateTime(A, B) | xs:dateTime |
A - B | xs:dateTime | xs:dayTimeDuration | op:subtract-dayTimeDuration-from-dateTime(A, B) | xs:dateTime |
A - B | xs:yearMonthDuration | xs:yearMonthDuration | op:subtract-yearMonthDurations(A, B) | xs:yearMonthDuration |
A - B | xs:dayTimeDuration | xs:dayTimeDuration | op:subtract-dayTimeDurations(A, B) | xs:dayTimeDuration |
A * B | numeric | numeric | op:numeric-multiply(A, B) | numeric |
A * B | xs:yearMonthDuration | numeric | op:multiply-yearMonthDuration(A, B) | xs:yearMonthDuration |
A * B | numeric | xs:yearMonthDuration | op:multiply-yearMonthDuration(B, A) | xs:yearMonthDuration |
A * B | xs:dayTimeDuration | numeric | op:multiply-dayTimeDuration(A, B) | xs:dayTimeDuration |
A * B | numeric | xs:dayTimeDuration | op:multiply-dayTimeDuration(B, A) | xs:dayTimeDuration |
A idiv B | numeric | numeric | op:numeric-integer-divide(A, B) | xs:integer |
A div B | numeric | numeric | op:numeric-divide(A, B) | numeric; but xs:decimal if both operands are xs:integer |
A div B | xs:yearMonthDuration | numeric | op:divide-yearMonthDuration(A, B) | xs:yearMonthDuration |
A div B | xs:dayTimeDuration | numeric | op:divide-dayTimeDuration(A, B) | xs:dayTimeDuration |
A div B | xs:yearMonthDuration | xs:yearMonthDuration | op:divide-yearMonthDuration-by-yearMonthDuration (A, B) | xs:decimal |
A div B | xs:dayTimeDuration | xs:dayTimeDuration | op:divide-dayTimeDuration-by-dayTimeDuration (A, B) | xs:decimal |
A mod B | numeric | numeric | op:numeric-mod(A, B) | numeric |
A eq B | numeric | numeric | op:numeric-equal(A, B) | xs:boolean |
A eq B | xs:boolean | xs:boolean | op:boolean-equal(A, B) | xs:boolean |
A eq B | xs:string | xs:string | op:numeric-equal(fn:compare(A, B), 0) | xs:boolean |
A eq B | xs:date | xs:date | op:date-equal(A, B) | xs:boolean |
A eq B | xs:time | xs:time | op:time-equal(A, B) | xs:boolean |
A eq B | xs:dateTime | xs:dateTime | op:dateTime-equal(A, B) | xs:boolean |
A eq B | xs:duration | xs:duration | op:duration-equal(A, B) | xs:boolean |
A eq B | Gregorian | Gregorian | op:gYear-equal(A, B) etc. | xs:boolean |
A eq B | xs:hexBinary | xs:hexBinary | op:hexBinary-equal(A, B) | xs:boolean |
A eq B | xs:base64Binary | xs:base64Binary | op:base64Binary-equal(A, B) | xs:boolean |
A eq B | xs:anyURI | xs:anyURI | op:numeric-equal(fn:compare(A, B), 0) | xs:boolean |
A eq B | xs:QName | xs:QName | op:QName-equal(A, B) | xs:boolean |
A eq B | xs:NOTATION | xs:NOTATION | op:NOTATION-equal(A, B) | xs:boolean |
A ne B | numeric | numeric | fn:not(op:numeric-equal(A, B)) | xs:boolean |
A ne B | xs:boolean | xs:boolean | fn:not(op:boolean-equal(A, B)) | xs:boolean |
A ne B | xs:string | xs:string | fn:not(op:numeric-equal(fn:compare(A, B), 0)) | xs:boolean |
A ne B | xs:date | xs:date | fn:not(op:date-equal(A, B)) | xs:boolean |
A ne B | xs:time | xs:time | fn:not(op:time-equal(A, B)) | xs:boolean |
A ne B | xs:dateTime | xs:dateTime | fn:not(op:dateTime-equal(A, B)) | xs:boolean |
A ne B | xs:duration | xs:duration | fn:not(op:duration-equal(A, B)) | xs:boolean |
A ne B | Gregorian | Gregorian | fn:not(op:gYear-equal(A, B)) etc. | xs:boolean |
A ne B | xs:hexBinary | xs:hexBinary | fn:not(op:hexBinary-equal(A, B)) | xs:boolean |
A ne B | xs:base64Binary | xs:base64Binary | fn:not(op:base64Binary-equal(A, B)) | xs:boolean |
A ne B | xs:anyURI | xs:anyURI | fn:not(op:numeric-equal(fn:compare(A, B), 0)) | xs:boolean |
A ne B | xs:QName | xs:QName | fn:not(op:QName-equal(A, B)) | xs:boolean |
A ne B | xs:NOTATION | xs:NOTATION | fn:not(op:NOTATION-equal(A, B)) | xs:boolean |
A gt B | numeric | numeric | op:numeric-greater-than(A, B) | xs:boolean |
A gt B | xs:boolean | xs:boolean | op:boolean-greater-than(A, B) | xs:boolean |
A gt B | xs:string | xs:string | op:numeric-greater-than(fn:compare(A, B), 0) | xs:boolean |
A gt B | xs:date | xs:date | op:date-greater-than(A, B) | xs:boolean |
A gt B | xs:time | xs:time | op:time-greater-than(A, B) | xs:boolean |
A gt B | xs:dateTime | xs:dateTime | op:dateTime-greater-than(A, B) | xs:boolean |
A gt B | xs:yearMonthDuration | xs:yearMonthDuration | op:yearMonthDuration-greater-than(A, B) | xs:boolean |
A gt B | xs:dayTimeDuration | xs:dayTimeDuration | op:dayTimeDuration-greater-than(A, B) | xs:boolean |
A gt B | xs:anyURI | xs:anyURI | op:numeric-greater-than(fn:compare(A, B), 0) | xs:boolean |
A lt B | numeric | numeric | op:numeric-less-than(A, B) | xs:boolean |
A lt B | xs:boolean | xs:boolean | op:boolean-less-than(A, B) | xs:boolean |
A lt B | xs:string | xs:string | op:numeric-less-than(fn:compare(A, B), 0) | xs:boolean |
A lt B | xs:date | xs:date | op:date-less-than(A, B) | xs:boolean |
A lt B | xs:time | xs:time | op:time-less-than(A, B) | xs:boolean |
A lt B | xs:dateTime | xs:dateTime | op:dateTime-less-than(A, B) | xs:boolean |
A lt B | xs:yearMonthDuration | xs:yearMonthDuration | op:yearMonthDuration-less-than(A, B) | xs:boolean |
A lt B | xs:dayTimeDuration | xs:dayTimeDuration | op:dayTimeDuration-less-than(A, B) | xs:boolean |
A lt B | xs:anyURI | xs:anyURI | op:numeric-less-than(fn:compare(A, B), 0) | xs:boolean |
A ge B | numeric | numeric | op:numeric-greater-than(A, B) or op:numeric-equal(A, B) | xs:boolean |
A ge B | xs:boolean | xs:boolean | fn:not(op:boolean-less-than(A, B)) | xs:boolean |
A ge B | xs:string | xs:string | op:numeric-greater-than(fn:compare(A, B), -1) | xs:boolean |
A ge B | xs:date | xs:date | fn:not(op:date-less-than(A, B)) | xs:boolean |
A ge B | xs:time | xs:time | fn:not(op:time-less-than(A, B)) | xs:boolean |
A ge B | xs:dateTime | xs:dateTime | fn:not(op:dateTime-less-than(A, B)) | xs:boolean |
A ge B | xs:yearMonthDuration | xs:yearMonthDuration | fn:not(op:yearMonthDuration-less-than(A, B)) | xs:boolean |
A ge B | xs:dayTimeDuration | xs:dayTimeDuration | fn:not(op:dayTimeDuration-less-than(A, B)) | xs:boolean |
A ge B | xs:anyURI | xs:anyURI | op:numeric-greater-than(fn:compare(A, B), -1) | xs:boolean |
A le B | numeric | numeric | op:numeric-less-than(A, B) or op:numeric-equal(A, B) | xs:boolean |
A le B | xs:boolean | xs:boolean | fn:not(op:boolean-greater-than(A, B)) | xs:boolean |
A le B | xs:string | xs:string | op:numeric-less-than(fn:compare(A, B), 1) | xs:boolean |
A le B | xs:date | xs:date | fn:not(op:date-greater-than(A, B)) | xs:boolean |
A le B | xs:time | xs:time | fn:not(op:time-greater-than(A, B)) | xs:boolean |
A le B | xs:dateTime | xs:dateTime | fn:not(op:dateTime-greater-than(A, B)) | xs:boolean |
A le B | xs:yearMonthDuration | xs:yearMonthDuration | fn:not(op:yearMonthDuration-greater-than(A, B)) | xs:boolean |
A le B | xs:dayTimeDuration | xs:dayTimeDuration | fn:not(op:dayTimeDuration-greater-than(A, B)) | xs:boolean |
A le B | xs:anyURI | xs:anyURI | op:numeric-less-than(fn:compare(A, B), 1) | xs:boolean |
A is B | node() | node() | op:is-same-node(A, B) | xs:boolean |
A << B | node() | node() | op:node-before(A, B) | xs:boolean |
A >> B | node() | node() | op:node-after(A, B) | xs:boolean |
A union B | node()* | node()* | op:union(A, B) | node()* |
A | B | node()* | node()* | op:union(A, B) | node()* |
A intersect B | node()* | node()* | op:intersect(A, B) | node()* |
A except B | node()* | node()* | op:except(A, B) | node()* |
A to B | xs:integer | xs:integer | op:to(A, B) | xs:integer* |
A , B | item()* | item()* | op:concatenate(A, B) | item()* |
Operator | Operand type | Function | Result type |
---|---|---|---|
+ A | numeric | op:numeric-unary-plus(A) | numeric |
- A | numeric | op:numeric-unary-minus(A) | numeric |
The tables in this section describe how values are assigned to the various components of the static context and dynamic context, and to the parameters that control the serialization process.
[Definition: The scope of a component is the context in which the component is associated with a value.] The following scopes are defined:
[Definition: If a component has global scope, then every expression in the query has the same value for that component, and it can not be overwritten by a module or by an expression.]
[Definition: If a component has module scope, then every expression in a given module has the same value for that component, and it can be overwritten or augmented for a given module.]
[Definition: If a component has lexical scope, then it is defined by a query expression, and its scope is defined by the semantics of the expression that defines it.]
[Definition: If a component has dynamic scope, then it is defined by a query expression, its scope is defined by the semantics of the expression that defines it, and run-time evaluation may influence its value.]
The following table describes the components of the static context. The following aspects of each component are described:
Default initial value: This is the initial value of the component if it is not overridden or augmented by the implementation or by a query.
Can be overwritten or augmented by implementation: Indicates whether an XQuery implementation is allowed to replace the default initial value of the component by a different, implementation-defined value and/or to augment the default initial value by additional implementation-defined values.
Can be overwritten or augmented by a query: Indicates whether a query is allowed to replace and/or augment the initial value provided by default or by the implementation. If so, indicates how this is accomplished (for example, by a declaration in the prolog).
Scope: the scope of the component.
Consistency Rules: Indicates rules that must be observed in assigning values to the component. Additional consistency rules may be found in 2.2.5 Consistency Constraints.
Component | Default initial value | Can be overwritten or augmented by implementation? | Can be overwritten or augmented by a query? | Scope | Consistency rules |
---|---|---|---|---|---|
XPath 1.0 Compatibility Mode | false |
no | no | global | Must be false . |
Statically known namespaces | fn , xml , xs ,
xsi , local |
overwriteable and augmentable (except for
xml ) |
overwriteable and augmentable by prolog or element constructor | lexical | Only one namespace can be assigned to a given prefix per lexical scope. |
Default element/type namespace | no namespace | overwriteable | overwriteable by prolog or element constructor | lexical | Only one default namespace per lexical scope. |
Default function namespace | fn |
overwriteable (not recommended) | overwriteable by prolog | module | None. |
In-scope schema types | built-in types in xs |
augmentable | augmentable by schema import in prolog | module | Only one definition per global or local type. |
In-scope element declarations | none | augmentable | augmentable by schema import in prolog | module | Only one definition per global or local element name. |
In-scope attribute declarations | none | augmentable | augmentable by schema import in prolog | module | Only one definition per global or local attribute name. |
In-scope variables | none | augmentable | overwriteable and augmentable by prolog and by variable-binding expressions | lexical | Only one definition per variable per lexical scope. |
Context item static type | none | overwriteable | overwriteable via a context item declaration, and by expresssions that set the context item | lexical | None. |
Function signatures | functions in fn namespace, and constructors for
built-in atomic types |
augmentable | augmentable by module import and by function declaration in prolog; augmentable by schema import (which adds constructor functions for user-defined types) | module | Each function must have a unique expanded QName and number of arguments. |
Statically known collations | only the default collation | augmentable | no | module | Each URI uniquely identifies a collation. |
Default collation | Unicode codepoint collation | overwriteable | overwriteable by prolog | module | None. |
Construction mode | preserve |
overwriteable | overwriteable by prolog | module | Value must be preserve or strip . |
Ordering mode | ordered |
overwriteable | overwriteable by prolog or expression | lexical | Value must be ordered or
unordered . |
Default order for empty sequences | implementation-defined | overwriteable | overwriteable by prolog | module | Value must be greatest or least . |
Boundary-space policy | strip |
overwriteable | overwriteable by prolog | module | Value must be preserve or strip . |
Copy-namespaces mode | inherit, preserve |
overwriteable | overwriteable by prolog | module | Value consists of inherit or
no-inherit , and preserve or
no-preserve . |
Static Base URI | See rules in 4.5 Base URI Declaration | overwriteable | overwriteable by prolog | module | Value must be a valid lexical representation of the type xs:anyURI. |
Statically known documents | none | augmentable | no | module | None. |
Statically known collections | none | augmentable | no | module | None. |
Statically known default collection type | node()* |
overwriteable | no | module | None. |
Serialization Parameters | |||||
byte-order-mark | implementation-defined | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
cdata-section-elements | empty | overwriteable and augmentable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
doctype-public | none | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
doctype-system | none | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
encoding | implementation-defined choice between "utf-8" and "utf-16" | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
escape-uri-attributes | (not applicable when method = xml) | overwriteable and augmentable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
include-content-type | (not applicable when method = xml) | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
indent | no | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
media-type | implementation-defined | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
method | xml | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
normalization-form | implementation-defined | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
omit-xml-declaration | implementation-defined | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
standalone | implementation-defined | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
suppress-indentation | empty | overwriteable and augmentable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
undeclare-prefixes | no | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
use-character-maps | empty | overwriteable and augmentable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
version | implementation-defined | overwriteable | overwriteable by prolog | module | Section 3 Serialization Parameters SER30 |
The following table describes the components of the dynamic context. The following aspects of each component are described:
Default initial value: This is the initial value of the component if it is not overridden or augmented by the implementation or by a query.
Can be overwritten or augmented by implementation: Indicates whether an XQuery implementation is allowed to replace the default initial value of the component by a different implementation-defined value and/or to augment the default initial value by additional implementation-defined values.
Can be overwritten or augmented by a query: Indicates whether a query is allowed to replace and/or augment the initial value provided by default or by the implementation. If so, indicates how this is accomplished.
Scope: the scope of the component.
Consistency Rules: Indicates rules that must be observed in assigning values to the component. Additional consistency rules may be found in 2.2.5 Consistency Constraints.
Component | Default initial value | Can be overwritten or augmented by implementation? | Can be overwritten or augmented by a query? | Scope | Consistency rules |
---|---|---|---|---|---|
Context item | none | overwriteable | overwritten during evaluation of path expressions and predicates - initial value may be overwritten with a context item declaration. | dynamic | None |
Context position | none | overwriteable | overwritten during evaluation of path expressions and predicates | dynamic | If context item is defined, context position must be >0 and <= context size; else context position is undefined. |
Context size | none | overwriteable | overwritten during evaluation of path expressions and predicates | dynamic | If context item is defined, context size must be >0; else context size is undefined. |
Dynamic Base URI | implementation-dependent | overwriteable | none | global | none |
Variable values | none | augmentable | overwriteable and augmentable by prolog and by variable-binding expressions | dynamic | Names and values must be consistent with in-scope variables. |
Function implementations | functions in fn namespace, and constructors for
built-in atomic types |
augmentable | augmentable by module import and by function declaration in prolog; augmentable by schema import (which adds constructor functions for user-defined types) | global | Must be consistent with function signatures |
Current dateTime | none | must be initialized by implementation | no | global | Must include a timezone. Remains constant during evaluation of a query. |
Implicit timezone | none | must be initialized by implementation | no | global | Remains constant during evaluation of a query. |
Available documents | none | must be initialized by implementation | no | global | None |
Available collections | none | must be initialized by implementation | no | global | None |
Default collection | none | overwriteable | no | global | None |
The following items in this specification are implementation-defined:
The version of Unicode that is used to construct expressions.
The implicit timezone.
The circumstances in which warnings are raised, and the ways in which warnings are handled.
The method by which errors are reported to the external processing environment.
Whether the implementation is based on the rules of [XML 1.0] and [XML Names] or the rules of [XML 1.1] and [XML Names 1.1]. One of these sets of rules must be applied consistently by all aspects of the implementation. If the implementation is based on the rules of [XML 1.0], the edition used must be at least Third Edition; the edition used is implementation-defined, but we recommend that implementations use the latest version.
How XDM instances are created from sources other than an Infoset or PSVI.
Any components of the static context or dynamic context that are overwritten or augmented by the implementation.
The default handling of empty sequences returned by an ordering
key (orderspec) in an order by
clause (empty
least
or empty greatest
).
The names and semantics of any extension expressions (pragmas) recognized by the implementation.
The names and semantics of any option declarations recognized by the implementation.
Protocols (if any) by which parameters can be passed to an external function, and the result of the function can returned to the invoking query.
The process by which the specific modules to be imported by a module import are identified, if the Module Feature is supported (includes processing of location hints, if any.)
The means by which serialization is invoked, if the Serialization Feature is supported.
The default values for the byte-order-mark
,
encoding
, media-type
,
normalization-form
, omit-xml-declaration
,
standalone
, and version
parameters, if
the Serialization Feature is
supported.
The result of an unsuccessful call to an external function (for example, if the function implementation cannot be found or does not return a value of the declared type).
Limits on ranges of values for various data types, as enumerated in 5.3 Data Model Conformance.
Syntactic extensions to XQuery, including both their syntax and semantics, as discussed in 5.4 Syntax Extensions.
Whether the type system is based on [XML Schema 1.0] or [XML Schema 1.1]. An implementation that has based its type system on XML Schema 1.0 is not required to support the use of the xs:dateTimeStamp constructor or the use of xs:dateTimeStamp as TypeName in any expression.
Note:
Additional implementation-defined items are listed in [XQuery and XPath Data Model (XDM) 3.0] and [XQuery and XPath Functions and Operators 3.0].
It is a static error if analysis of an expression relies on some component of the static context that has not been assigned a value.
It is a dynamic error if evaluation of an expression relies on some part of the dynamic context that has not been assigned a value.
It is a static error if an expression is not a valid instance of the grammar defined in A.1 EBNF.
It is a type error if, during the static analysis phase, an expression is found to have a static type that is not appropriate for the context in which the expression occurs, or during the dynamic evaluation phase, the dynamic type of a value does not match a required type as specified by the matching rules in 2.5.5 SequenceType Matching.
During the analysis phase, it is a static error if the static type assigned to an expression
other than the expression ()
or data(())
is empty-sequence()
.
(Not currently used.)
(Not currently used.)
It is a static error if an expression refers to an element name, attribute name, schema type name, namespace prefix, or variable name that is not defined in the static context, except for an ElementName in an ElementTest or an AttributeName in an AttributeTest.
An implementation that does not support the Schema Import Feature must raise a static error if a Prolog contains a schema import.
An implementation must raise a static error if it encounters a reference to an axis that it does not support.
It is a static error if the set of definitions contained in all schemas imported by a Prolog do not satisfy the conditions for schema validity specified in Sections 3 and 5 of Part 1 of [XML Schema 1.0] or [XML Schema 1.1] --i.e., each definition must be valid, complete, and unique.
It is a static error if an implementation recognizes a pragma but determines that its content is invalid.
(Not currently used.)
(Not currently used.)
An implementation that does not support the Module Feature raises a static error if it encounters a module declaration or a module import.
It is a static error if the expanded QName and number of arguments in a function call do not match the name and arity of a function signature in the static context.
It is a type error if the result of the last step in a path expression contains both nodes and non-nodes.
It is a type error if the result of a step (other than the last step) in a path expression is not a sequence of nodes.
It is a type error if, in an axis step, the context item is not a node.
(Not currently used.)
It is a static error if a namespace declaration attribute contains an EnclosedExpr.
(Not currently used.)
It is a type error if the content sequence in an element constructor contains an attribute node following a node that is not an attribute node.
It is a dynamic error if any attribute of a constructed element does not have a name that is distinct from the names of all other attributes of the constructed element.
It is a dynamic error if the result of the content
expression of a computed processing instruction constructor
contains the string "?>
".
In a validate expression, it is a dynamic error if the root element
information item in the PSVI resulting from validation does not
have the expected validity property: valid
if
validation mode is strict
, or either
valid
or notKnown
if validation mode is
lax
.
(Not currently used.)
(Not currently used.)
It is a type
error if the argument of a validate
expression
does not evaluate to exactly one document or element node.
It is a static error if the version number specified in a version declaration is not supported by the implementation.
A static error is raised if a Prolog contains more than one base URI declaration.
It is a static error if a module contains multiple bindings for the same namespace prefix.
It is a static
error if multiple functions declared or
imported by a module
have the same number of arguments and their expanded QNames are
equal (as defined by the eq
operator).
It is a static error to import two schema components that both define the same name in the same symbol space and in the same scope.
(Not currently used.)
(Not currently used.)
It is a static error if a Prolog contains more than one default collation declaration, or the value specified by a default collation declaration is not present in statically known collations.
It is a static error for a function declaration to have more than one parameter with the same name.
It is a static error if the attributes specified by a direct element constructor do not have distinct expanded QNames.
It is a dynamic error if the value of the name
expression in a computed processing instruction constructor cannot
be cast to the type xs:NCName
.
(Not currently used.)
(Not currently used.)
It is a dynamic error the node-name of a node constructed by a computed attribute constructor has any of the following properties:
Its namespace prefix is xmlns
.
It has no namespace prefix and its local name is
xmlns
.
Its namespace URI is
http://www.w3.org/2000/xmlns/
.
Its namespace prefix is xml
and its namespace URI
is not http://www.w3.org/XML/1998/namespace
.
Its namespace prefix is other than xml
and its
namespace URI is
http://www.w3.org/XML/1998/namespace
.
It is a static
error if the function name in a function declaration is in one
of the following namespaces:
http://www.w3.org/XML/1998/namespace,
http://www.w3.org/2001/XMLSchema,
http://www.w3.org/2001/XMLSchema-instance,
http://www.w3.org/2005/xpath-functions
,
http://www.w3.org/2005/xpath-functions/math
.
An implementation MAY raise a static error if the value of a URILiteral is of nonzero length and
is not in the lexical space of xs:anyURI
.
It is a static error if multiple module imports in the same Prolog specify the same target namespace.
It is a static error if a function or variable declared in a library module is not in the target namespace of the library module.
It is a static
error if two or more variables declared or imported by a
module have equal expanded QNames (as
defined by the eq
operator.)
It is a dynamic error if the dynamic type of the
operand of a treat
expression does not match the
sequence type
specified by the treat
expression. This error might
also be raised by a path expression beginning with "/
"
or "//
" if the context node is not in a tree that is
rooted at a document node. This is because a leading
"/
" or "//
" in a path expression is an
abbreviation for an initial step that includes the clause
treat as document-node()
.
It is a static error if the expanded QName for an AtomicOrUnionType in a SequenceType is not defined in the in-scope schema types as an atomic type or a union type.
(Not currently used.)
(Not currently used.)
It is a static error if a variable depends on itself.
It is a static error if a Prolog contains more than one copy-namespaces declaration.
(Not currently used.)
It is a static error if a schema import binds a namespace prefix but does not specify a target namespace other than a zero-length string.
It is a static error if multiple schema imports specify the same target namespace.
It is a static error if an implementation is unable to process a schema or module import by finding a schema or module with the specified target namespace.
It is a static error if the name of a function in a function declaration is not in a namespace (expanded QName has a null namespace URI).
It is a dynamic error if the operand of a validate expression is a document node whose children do not consist of exactly one element node and zero or more comment and processing instruction nodes, in any order.
(Not currently used.)
(Not currently used.)
It is a dynamic error if the value of the name expression in a computed processing instruction constructor is equal to "XML" (in any combination of upper and lower case).
A static error is raised if a Prolog contains more than one ordering mode declaration.
A static error is raised if a Prolog contains more than one default element/type namespace declaration, or more than one default function namespace declaration.
A static error is raised if a Prolog contains more than one construction declaration.
A static error is raised if a Prolog contains more than one boundary-space declaration.
A static error is raised if a Prolog contains more than one empty order declaration.
A static
error is raised if one of the predefined prefixes
xml
or xmlns
appears in a namespace
declaration, or if any of the following conditions is statically
detected in any expression or declaration:
The prefix xml
is bound to some namespace URI other
than http://www.w3.org/XML/1998/namespace
.
A prefix other than xml
is bound to the namespace
URI http://www.w3.org/XML/1998/namespace
.
The prefix xmlns
is bound to any namespace URI.
A prefix other than xmlns
is bound to the namespace
URI http://www.w3.org/2000/xmlns/
.
A static error is raised if the namespace declaration attributes of a direct element constructor do not have distinct names.
It is a dynamic error if the result of the content expression of a computed comment constructor contains two adjacent hyphens or ends with a hyphen.
(Not currently used.)
It is a dynamic error if the value of the name expression in a computed element or attribute constructor cannot be converted to an expanded QName (for example, because it contains a namespace prefix not found in statically known namespaces.)
An implementation that does not support the Validation Feature
must raise a static
error if it encounters a validate
expression.
It is a static
error if a collation
subclause in an order
by
clause of a FLWOR expression does not identify a
collation that is present in statically known collations.
(Not currently used.)
(Not currently used.)
It is a static error if an extension expression contains neither a pragma that is recognized by the implementation nor an expression enclosed in curly braces.
It is a static
error if the target type of a cast
or
castable
expression is xs:NOTATION
or
xs:anyAtomicType
.
It is a static error if a QName used in a query contains a namespace prefix that cannot be expanded into a namespace URI by using the statically known namespaces.
(Not currently used.)
(Not currently used.)
It is a dynamic error if the element validated by a
validate
statement does not have a top-level element
declaration in the in-scope element declarations, if validation
mode is strict
.
It is a static error if the namespace URI in a namespace declaration attribute is a zero-length string, and the implementation does not support [XML Names 1.1].
It is a type
error if the typed value of a copied element or attribute node
is namespace-sensitive when construction
mode is preserve
and copy-namespaces mode is
no-preserve
.
It is a static
error if the encoding specified in a Version Declaration does
not conform to the definition of EncName
specified in
[XML 1.0].
It is a static error if the literal that specifies the target namespace in a module import or a module declaration is of zero length.
It is a static
error if a variable bound in a for
or
window
clause of a FLWOR expression, and its
associated positional variable, do not have distinct names
(expanded
QNames).
It is a static error if a character reference does not identify a valid character in the version of XML that is in use.
An implementation MAY raise a
dynamic error
if an xml:id
error, as defined in [XML ID], is encountered during construction of an
attribute named xml:id
.
An implementation MAY raise a
dynamic error
if a constructed attribute named xml:space
has a value
other than preserve
or default
.
In the group by
clause of a FLWOR expression, it is
a static error
if the name of a grouping variable is not equal (by the
eq
operator on expanded QNames) to the name of a variable
that is bound by a for
or let
clause that
precedes the group by
clause.
In the group by
clause of a FLWOR expression, it is
a dynamic
error if the value bound to a grouping variable consists of a
sequence of more than one item.
It is a dynamic error the node-name of a node constructed by a computed element constructor has any of the following properties:
Its namespace prefix is xmlns
.
Its namespace URI is
http://www.w3.org/2000/xmlns/
.
Its namespace prefix is xml
and its namespace URI
is not http://www.w3.org/XML/1998/namespace
.
Its namespace prefix is other than xml
and its
namespace URI is
http://www.w3.org/XML/1998/namespace
.
It is a static error for a decimal-format to specify a value that is not valid for a given property, as described in statically known decimal formats
It is a static error if, for any named or unnamed decimal format, the properties representing characters used in a picture string do not each have distinct values. These properties are decimal-separator-sign, grouping-separator, percent-sign, per-mille-sign, zero-digit, digit-sign, and pattern-separator-sign.
A ContextItemDecl
must not occur after an
expression that relies on the initial context item, and no query
may contain more than one ContextItemDecl.
(Not currently used.)
An error [err:XQDY0101] is raised if a computed namespace constructor attempts to do any of the following:
Bind the prefix xml
to some namespace URI other
than http://www.w3.org/XML/1998/namespace
.
Bind a prefix other than xml
to the namespace URI
http://www.w3.org/XML/1998/namespace
.
Bind the prefix xmlns
to any namespace URI.
Bind a prefix to the namespace URI
http://www.w3.org/2000/xmlns/
.
In an element constructor, if two or more namespace bindings in the in-scope bindings would have the same prefix, then an error is raised if they have different URIs; if they would have the same prefix and URI, duplicate bindings are ignored.
All variables in a window
clause must have distinct
names.
A TypeName that is
specified in a validate
expression must be found in
the in-scope
schema definitions
It is a type error if the content sequence in an element constructor contains a function item.
It is a static
error if a function's annotations contain more than one
annotation named %private
or %public
.
It is a static error if the initializer of the context item depends on the context item.
It is a static error if an output declaration occurs in a library module.
It is a static
error if the local name of an output declaration in the
http://www.w3.org/2010/xslt-xquery-serialization
namespace is not one of the serialization parameter names listed in
C.1 Static Context
Components.
It is a static error if the same serialization parameter is used more than once in an output declaration.
It is a static error for a query prolog to contain two decimal formats with the same name, or to contain two default decimal formats. [err:XQST0111].
It is a static error to partially apply or create a function item for a function which accesses the focus [err:XPST0112].
Specifying a VarValue or VarDefaultValue for a context item declaration in a library module is a static error.
It is a static error for a decimal format declaration to define the same property more than once [err:XQST0114].
It is a static error if the document specified by the option "http://www.w3.org/2010/xslt-xquery-serialization":parameter-document raises a serialization error.
It is a static
error if a variable declaration's annotations contain more than
one annotation named %private
or
%public
.
Attempt to cast to a namespace-sensitive type failed because the namespace bindings for the result can not be determined.
In a direct element constructor, the name used in the end tag must exactly match the name used in the corresponding start tag, including its prefix or absence of a prefix.
It is a static error if the implementation is not able to
process the value of an output:parameter-document
declaration to produce an XDM instance.
application/xquery
Media TypeThis Appendix specifies the media type for XQuery Version 1.0. XQuery is a language for querying over collections of data from XML data sources, as specified in the main body of this document. This media type is being submitted to the IESG (Internet Engineering Steering Group) for review, approval, and registration with IANA (Internet Assigned Numbers Authority.)
This document, found at http://www.w3.org/TR/xquery/,
together with its normative references, defines the language XQuery
Version 1.0. This Appendix provides information about the
application/xquery
media type, which is intended to be
used for transmitting queries written in the XQuery language.
This document was prepared by members of the W3C XML Query Working Group. Please send comments to public-qt-comments@w3.org, a public mailing list with archives at http://lists.w3.org/Archives/Public/public-qt-comments.
application/xquery
MIME media type name: application
MIME subtype name: xquery
Required parameters: none
Optional parameters: none
The syntax of XQuery is expressed in Unicode but may be written
with any Unicode-compatible character encoding, including UTF-8 or
UTF-16, or transported as US-ASCII or ISO-8859-1 with Unicode
characters outside the range of the given encoding represented
using an XML-style ෝ
syntax.
The public XQuery Web page lists more than two dozen implementations of the XQuery language, both proprietary and open source.
This new media type is being registered to allow for deployment of XQuery on the World Wide Web.
The most common file extensions in use for XQuery are
.xq
and .xquery
.
The appropriate Macintosh file type code is
TEXT
.
For use with transports that are not 8-bit clean, quoted-printable encoding is recommended since the XQuery syntax itself uses the US-ASCII-compatible subset of Unicode.
An XQuery document may contain an encoding declaration as part of its version declaration:
xquery version "1.0" encoding "utf-8";
An XQuery file may have the string xquery version
"V.V"
near the beginning of the document, where
"V.V"
is a version number. Currently the version
number, if present, must be "1.0"
.
XQuery documents use the Unicode character set and, by default, the UTF-8 encoding.
Queries written in XQuery may cause arbitrary URIs or IRIs to be
dereferenced. Therefore, the security issues of [RFC3987] Section 8 should be considered. In
addition, the contents of resources identified by
file:
URIs can in some cases be accessed, processed
and returned as results. XQuery expressions can invoke any of the
functions defined in [XQuery and
XPath Functions and Operators 3.0]. For example, the
fn:doc()
and fn:doc-available()
functions
allow local filesystem probes as well as access to any URI-defined
resource accessible from the system evaluating the XQuery
expression.
XQuery is a full declarative programming language, and supports user-defined functions, external function libraries (modules) referenced by URI, and system-specific "native" functions.
Arbitrary recursion is possible, as is arbitrarily large memory usage, and implementations may place limits on CPU and memory usage, as well as restricting access to system-defined functions.
The XML Query Working group is working on a facility to allow XQuery expressions to create and update persistent data. Untrusted queries should not be given write access to data.
Furthermore, because the XQuery language permits extensions, it
is possible that application/xquery
may describe
content that has security implications beyond those described
here.
Dynamic Base URI. This is an absolute URI, used to resolve relative URIs during dynamic evaluation.
In the operator mapping tables, the term Gregorian refers
to the types xs:gYearMonth
, xs:gYear
,
xs:gMonthDay
, xs:gDay
, and
xs:gMonth
.
NaN specifies the string used for the NaN-symbol, which is used to represent the value NaN (not-a-number); the default value is the string "NaN"
A Prolog is a series of declarations and imports that define the processing environment for the module that contains the Prolog.
During evaluation of an expression, it is sometimes necessary to determine whether a value with a known dynamic type "matches" an expected sequence type. This process is known as SequenceType matching.
Static Base URI. This is an absolute URI, used to resolve relative URIs during static analysis.
Within this specification, the term URI refers to a Universal Resource Identifier as defined in [RFC3986] and extended in [RFC3987] with the new name IRI.
The term XDM instance is used, synonymously with the term value, to denote an unconstrained sequence of items in the data model.
An XPath 1.0 Processor processes a query according to the XPath 1.0 specification.
XPath 1.0 compatibility mode. This
component must be set by all host languages that include XPath 3.0
as a subset, indicating whether rules for compatibility with XPath
1.0 are in effect. XQuery sets the value of this component to
false
.
An XPath 2.0 Processor processes a query according to the XPath 2.0 specification.
An XPath 3.0 Processor processes a query according to the XPath 3.0 specification.
An XQuery 1.0 Processor processes a query according to the XQuery 1.0 specification.
An XQuery 3.0 Processor processes a query according to the XQuery 3.0 specification.
If an annotation is present in a FunctionTest, it is called an annotation assertion.
An argument to a function call is either an argument expression or an ArgumentPlaceholder ("?").
Argument expressions are evaluated, producing argument values.
An atomic value is a value in the value space of an atomic type, as defined in [XML Schema 1.0] or [XML Schema 1.1].
Atomization of a sequence is defined as the result of
invoking the fn:data
function on the sequence, as
defined in [XQuery and XPath
Functions and Operators 3.0].
Available collections. This is a mapping of strings to
sequences of nodes. The string represents the absolute URI of a
resource. The sequence of nodes represents the result of the
fn:collection
function when that URI is supplied as
the argument.
Available documents. This is a mapping of strings to
document nodes. The string represents the absolute URI of a
resource. The document node is the root of a tree that represents
that resource using the data model. The document node is returned by
the fn:doc
function when applied to that URI.
An axis step returns a sequence of nodes that are reachable from the context node via a specified axis. Such a step has two parts: an axis, which defines the "direction of movement" for the step, and a node test, which selects nodes based on their kind, name, and/or type annotation.
Base URI. This is an absolute URI, used when necessary to resolve a relative URI.
A base URI declaration specifies the Static Base URI property. The Static Base URI property is used when resolving relative URIs during static analysis.
In a for
clause or window
clause, when
an expression is preceded by the keyword in
, the value
of that expression is called a binding sequence.
Boundary whitespace is a sequence of consecutive
whitespace characters within the content of a direct
element constructor, that is delimited at each end either by
the start or end of the content, or by a DirectConstructor, or by an
EnclosedExpr. For this
purpose, characters generated by character references such as
 
or by CDataSections are not considered
to be whitespace characters.
A boundary-space declaration sets the boundary-space policy in the static context, overriding any implementation-defined default. Boundary-space policy controls whether boundary whitespace is preserved by element constructors during processing of the query.
Boundary-space policy. This component controls the processing of boundary whitespace by direct element constructors, as described in 3.8.1.4 Boundary Whitespace.
The built-in functions supported by XQuery 3.0 are defined in [XQuery and XPath Functions and Operators 3.0].
A character reference is an XML-style reference to a [Unicode] character, identified by its decimal or hexadecimal codepoint.
A collation is a specification of the manner in which strings and URIs are compared and, by extension, ordered. For a more complete definition of collation, see [XQuery and XPath Functions and Operators 3.0].
One way to construct a sequence is by using the comma operator, which evaluates each of its operands and concatenates the resulting sequences, in order, into a single result sequence.
A computed element constructor creates an element node, allowing both the name and the content of the node to be computed.
A construction declaration sets the construction mode in the static context, overriding any implementation-defined default.
Construction mode. The construction mode governs the
behavior of element and document node constructors. If construction
mode is preserve
, the type of a constructed element
node is xs:anyType
, and all attribute and element
nodes copied during node construction retain their original types.
If construction mode is strip
, the type of a
constructed element node is xs:untyped
; all element
nodes copied during node construction receive the type
xs:untyped
, and all attribute nodes copied during node
construction receive the type xs:untypedAtomic
.
The constructor function for a given type is used to
convert instances of other atomic types into the given type. The
semantics of the constructor function call T($arg)
are
defined to be equivalent to the expression (($arg) cast as
T?)
.
The final part of a computed constructor is an expression enclosed in braces, called the content expression of the constructor, that generates the content of the node.
The context item is the item currently being processed.
Context item static type. This component defines the static type of the context item within the scope of a given expression.
When the context item is a node, it can also be referred to as the context node.
The context position is the position of the context item within the sequence of items currently being processed.
The context size is the number of items in the sequence of items currently being processed.
A copy-namespaces declaration sets the value of copy-namespaces mode in the static context, overriding any implementation-defined default. Copy-namespaces mode controls the namespace bindings that are assigned when an existing element node is copied by an element constructor or document constructor.
Copy-namespaces mode. This component controls the
namespace bindings that are assigned when an existing element node
is copied by an element constructor, as described in 3.8.1 Direct Element
Constructors. Its value consists of two parts:
preserve
or no-preserve
, and
inherit
or no-inherit
.
Current dateTime. This information represents an
implementation-dependent point
in time during the processing of a
query, and includes an explicit timezone. It can be
retrieved by the fn:current-dateTime
function. If
invoked multiple times during the execution of a query, this function always returns the same
result.
XQuery 3.0 operates on the abstract, logical structure of an XML document, rather than its surface syntax. This logical structure, known as the data model, is defined in [XQuery and XPath Data Model (XDM) 3.0].
For a given node in an XDM instance, the data model schema is defined as the schema from which the type annotation of that node was derived.
A decimal-format declaration adds a decimal format to the
statically known decimal formats,
which define the properties used to format numbers using the
fn:format-number()
function
decimal-separator specifies the character used for the decimal-separator-sign; the default value is the period character (.)
Default collation. This identifies one of the collations
in statically known collations as the
collation to be used by functions and operators for comparing and
ordering values of type xs:string
and
xs:anyURI
(and types derived from them) when no
explicit collation is specified.
A default collation declaration sets the value of the default collation in the static context, overriding any implementation-defined default.
Default collection. This is the sequence of nodes that
would result from calling the fn:collection
function
with no arguments.
Default element/type namespace. This is a namespace URI or absentDM30. The namespace URI, if present, is used for any unprefixed QName appearing in a position where an element or type name is expected.
Default function namespace. This is a namespace URI or absentDM30. The namespace URI, if present, is used for any unprefixed QName appearing in a position where a function name is expected.
Default order for empty sequences. This component
controls the processing of empty sequences and NaN
values as ordering keys in an order by
clause in a
FLWOR expression, as described in 3.9.8 Order By Clause.
The delimiting terminal symbols are: S, "!=", StringLiteral, "#", "#)", "$", "%", "(", "(#", ")", "*", "+", (comma), "-", "-->", (dot), "..", "/", "//", "/>", (colon), "::", ":=", (semi-colon), "<", "<!--", "<![CDATA[", "</", "<<", "<=", "<?", "=", ">", ">=", ">>", "?", "?>", "@", "[", "]", "]]>", "{", "|", "}"
An expression E
depends on a function if any
of the following is true:
|
An expression E
depends on a variable
V
if any of the following is true:
|
A deterministic function is a function that always evaluates to the same result if it is invoked multiple times with the same arguments during the evaluation of a query.
digi