Status of this Document
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 a Working
Group Note as described in the Process
Document. It was developed by the W3C XML Query Working Group, which
is part of the XML
Activity.
These Requirements identify extensions to the XQuery 1.0 Recommendation,
published 23 January 2007, that have been requested by WG
participants and by reviewers who do not participate in the W3C
activities. The XML Query WG has reviewed these requirements and
accepted them to the degree reflected in this document.
No substantive changes have been made to this specification
since its previous publication as a Working Draft.
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 “[XQuery30Req]”
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
Group Note 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 Goals
The goal of XML Query 3.0 is to extend XML Query 1.0 with
additional functionality in response to requests from users and
implementors.
Satisfying these goals may require changes to the set of seven
documents that have progressed to Recommendation together (Data
Model, Functions and Operators, Serialization, XPath 2.0, XQuery
1.0, XQueryX, and XSLT 2.0).
2
Requirements
2.1 Terminology
The following keywords are used throughout the document to
specify the extent to which an item is a requirement for the work
of the XML Query Working Group:
- MUST
-
The item is an absolute requirement.
- SHOULD
-
There may exist valid reasons not to treat this item as a
requirement, but the full implications should be understood and the
case carefully weighed before discarding this item.
- MAY
-
An item deserves attention, but further study is needed to
determine whether the item should be treated as a requirement.
When the words MUST, SHOULD, or MAY are used in this technical sense
[IETF RFC 2119],
they occur as a hyperlink to these definitions. These words will
also be used with their conventional English meaning, in which case
there is no hyperlink. For instance, the phrase "the full
implications should be understood" uses the word "should" in its
conventional English sense, and therefore occurs without the
hyperlink.
Each requirement also includes a status section,
indicating its current situation in the XQuery/XPath/XSLT family of
specifications. Three status levels are used:
- "Green" status
-
This indicates that the requirement, according to
its original formulation, has been completely met. Optional
clarifying text may follow.
- "Yellow" status
-
This indicates that the requirement has been
partially met according to its original formulation. When this
happens, explanatory text is provided to better clarify the current
scope of the requirement.
- "Red" status
-
This indicates that the requirement, according to
its original formulation, has not been met. If this is the case,
explanatory text is provided.
2.2 General Requirements
2.2.1 Backward compatibility
-
XQuery 3.0 MUST be backward
compatible.
Every valid XQuery 1.0 expression MUST be valid in XQuery 3.0 and it MUST evaluate to the same result.
Status: this requirement has been
met.
2.3 XML Query Functionality
2.3.1 Value-based
grouping
-
XQuery 3.0 MUST include a
language facility to specify value-based grouping.
Status: this requirement has been
met.
2.3.2 Error processing and
recovery
-
XQuery 3.0 MUST provide a
mechanism to process errors raised by an expression and to return
an alternative value.
This MAY be implemented by
introducing a try-catch expression.
Status: this requirement has been
met.
2.3.3
Numeric formatting
-
XQuery 3.0 MUST include
additional library functions or an equivalent mechanism to perform
formatting of numeric values.
It SHOULD be similar to the
functionality provided in XSLT 2.0, such as
by function format-number().
Status: this requirement has been
met.
2.3.4 Date
formatting
-
XQuery 3.0 MUST include
additional library functions or an equivalent mechanism to perform
formatting of date and time values.
It SHOULD be similar to the
functionality provided in XSLT 2.0, such as
by functions format-date(),
format-time(), format-dateTime().
Status: this requirement has been
met.
2.3.5 Default values
for external variables
-
XQuery 3.0 MUST have a mechanism
to specify default values for external variables.
Status: this requirement has been
met.
2.3.6 Non-deterministic
external functions
-
XQuery 3.0 MUST provide a way to
denote that an external function is non-deterministic.
Status: this requirement has not been
met.
2.3.7 Positional grouping
-
XQuery 3.0 SHOULD provide a
facility for positional grouping of items in a sequence according
to specified partitioning conditions.
Status: this requirement has been
met.
2.3.8 Windowing
-
XQuery 3.0 SHOULD provide a
way to iterate over a sequence by several values at a time.
Status: this requirement has been
met.
2.3.9
Output numbering
-
XQuery 3.0 SHOULD provide a
mechanism to associate ordinal numbers with the items returned by a
FLWOR expression.
Status: this requirement has been
met.
2.3.10 Dynamic
creation of namespace bindings
-
XQuery 3.0 SHOULD allow
dynamic creation of namespace bindings.
Status: this requirement has been
met.
2.3.11 Declaration of
serialization parameters
-
XQuery 3.0 SHOULD have a
mechanism to specify serialization parameters in the query
prolog.
Status: this requirement has been
met.
2.3.12 Node
references
-
XQuery 3.0 SHOULD support
creation of a reference to an existing node having the following
properties:
a) the reference could be included in a constructed element
b) the reference can be dereferenced, returning the original
node with the original node id.
Status: this requirement has not been
met.
2.3.13 Outer for
-
XQuery 3.0 SHOULD provide
additional mechanisms to specify joins between sequences. A
possible approach would be to add an "outer-for" clause to
the FLWOR expression to specify variable binding which is
guaranteed to be bound to an empty sequence if there are no other
bindings generated.
Status: this requirement has been
met.
2.3.14 Type declaration for
context item
-
XQuery 3.0 SHOULD allow
explicit type declaration for the context item.
Status: this requirement has been
met.
2.3.15 Support for new data
types
-
XQuery 3.0 SHOULD support new
data types introduced in XML Schema
1.1.
Status: this requirement has been
met.
2.3.16 Higher order functions
-
XQuery 3.0 MAY provide an ability
to pass a function as an argument to another function and to invoke
a function that has been passed as an argument.
Status: this requirement has been met.
(The proposal is not yet integrated into our internal Working
Draft.)
XQuery 3.0 MAY also provide the
ability to define anonymous functions e.g., lambda expressions.
Status: this requirement has been met.
(The proposal is not yet integrated into our internal Working
Draft.)
2.3.17 Conditional constructors
-
XQuery 3.0 MAY add a language
extension to the node constructors to specify, in a compact
notation, that a node should be constructed only if its typed value
would not be an empty sequence or if it would satisfy some other
condition.
Status: this requirement is already met
by XQuery 1.0, there is no need to introduce new syntax. Either of
the following solutions works:
if ($mentor) then attribute mentor { $mentor } else ()
(attribute mentor { $mentor })[$mentor]
2.3.18 Validation
-
XQuery 3.0 MAY provide a
mechanism to validate an element or document node with respect to a
global named type
Status: this requirement has been
met.
or against non-global element declarations or types.
Status: this requirement has not been
met.
XQuery 3.0 MAY provide a
mechanism to validate an element or document node against a named
schema without importing the schema.
Status: this requirement has not been
met.
2.3.20 Module composition
restrictions
-
XQuery 3.0 MAY relax the
restrictions on the module import feature relating to forward
references and circular imports.
Status: this requirement has been
met.
2.3.21 Invocation of
external functionality
-
XQuery 3.0 MAY provide a
normative way to invoke external functions and modules that are not
implemented in XQuery, such as functions defined as web services or
XSLT functions and templates.
Status: this requirement has not been
met.
2.3.22 Static typing extensions
-
XQuery 3.0 MAY extend static
typing rules.
Status: this requirement has not been met.
Static typing is no longer a normative part of XQuery 3.0.
3 References
3.1 Normative
- XQuery 3.0: An XML Query Language
-
XQuery 3.0: An
XML Query Language, Jonathan Robie, Don Chamberlin,
Michael Dyck, John Snelson, Editors. World Wide Web Consortium, 08
April 2014. This version is
http://www.w3.org/TR/2014/REC-xquery-30-20140408/. The
latest version is available
at http://www.w3.org/TR/xquery-30/.
- XQuery and XPath Data Model (XDM)
3.0
-
XQuery and XPath
Data Model (XDM) 3.0, Norman Walsh, Anders Berglund,
John Snelson, Editors. World Wide Web Consortium, 08 April 2014.
This version is
http://www.w3.org/TR/2014/REC-xpath-datamodel-30-20140408/. The
latest
version is available at
http://www.w3.org/TR/xpath-datamodel-30/.
- XSL
Transformations (XSLT) Version 3.0
-
- XQuery Update
Facility 3.0 Requirements and Use Cases
-
- XQuery and XPath
Full Text 3.0 Requirements and Use Cases
-
- XQuery
1.0
-
- XSLT
2.0
-
- XDM
-
- XQuery 1.0
requirements
-
3.2 Non-normative
The following references are some of the works considered by the
WG in deriving its requirements.
- XML
-
- XML Schema Part 0
-
- XML Schema Part 1
-
- XML Schema Part 2
-
- XML Schema 1.1 requirements
-
- Kay06
-
"Positional Grouping in XQuery", Kay, M.H. XIME-P
International workshop proceedings, 2006
- Colby05
-
"Extending XQuery for Analytics", Beyer K., Chamberlin D. et
al. SIGMOD 2005
- Borkar04
-
"Extending XQuery for Grouping, Duplicate Elimination, and
Outer Joins.", Borkar V. and Carey M. XML 2004, Idealliance