XQuery 1.0 and XPath 2.0 Data Model

4.1.1 dm:base-uri Accessor

The dm:base-uri accessor returns a sequence containing zero or one uri references.

Document, element, and processing-instruction nodes have a base-uri property. If that property is non-empty, its value is returned.

If the accessor is called on a node that does not have a base-uri property, or whose base-uri property is empty, the base-uri of that node's parent is returned. If the node has no parent, an error is raised. See [Issue-0087: base-uri should return ()?]

4.1.2 node-kind Accessor

The dm:node-kind accessor returns a string value identifying the kind of node on which the accessor was called. One of the following values is returned:

• "document" for document nodes.

• "element" for element nodes.

• "attribute" for attribute nodes.

• "text" for text nodes.

• "namespace" for namespace nodes.

• "processing-instruction" for processing instruction nodes.

• "comment" for comment nodes.

4.1.3 node-name Accessor

The dm:node-name accessor returns a sequence of zero or one xs:QNames.

• For element and attribute nodes, dm:node-name returns the qualified name of the element or attribute.

• For processing-instructions nodes, dm:node-name returns an xs:QName with a the processing instruction target name in the local-name and no namespace URI.

• For namespace nodes, dm:node-name returns an xs:QName with the prefix of the namespace declaration in the local-name and no namespace URI. If the namespace declaration declares the default namespace, which has no prefix, an empty sequence is returned.

  Some implementations may not preserve information about the prefixes declared. In these cases, the dm:node-name accessor returns the empty sequence when applied to processing-instruction nodes.

4.1.4 parent Accessor

The dm:parent accessor returns a sequence containing zero or one nodes.

For nodes that have a parent, dm:parent returns the parent node. For all other nodes, it returns the empty sequence.

If the return value is not the empty sequence, it will always be either an element node or a document node.

4.1.5 string-value Accessor

The dm:string-value accessor returns a string representation of the node.

For some kinds of nodes, this is part of the node; for other kinds of nodes, it is computed from the dm:string-value of its descendant nodes.

The dm:string-value accessor can be used to recover the lexical representation of an atomic value. The details of converting an atomic value to its string representation are described in the "Casting Functions" section of [XQuery 1.0 and XPath 2.0 Functions and Operators]. In particular if the atomic value's type is primitive, dm:string-value returns the atomic value's canonical lexical representation for that primitive type as specified in [XMLSchema Part 2]. If the atomic value's type is derived, the lexical representation depends on whether a value is supplied for the type's pattern facet: If no such value is supplied dm:string-value returns the atomic value's canonical lexical representation for the primitive base type. Otherwise dm:string-value returns a lexical representation that matches the value specified for the pattern facet. (This case includes xs:integers.) See [Issue-0072: Lexical representation of Schema primitive types].

4.1.6 typed-value Accessor

The dm:typed-value accessor returns the typed-value of the node, which is a sequence of zero or more atomic values. The typed-value is closely related to the node's string-value and its type. For instance when the node's string-value is "3.14" and its type is xs:decimal, the typed-value is a sequence containing the atomic value 3.14 of type decimal. In fact, when the type is an atomic type, typed-value is always the atomic-value constructed from the string-value and the type.

In the general case, dm:typed-value constructs a sequence of atomic values. These values are derived from the string-value of the element and its type, in such a way as to be consistent with validation.

See [Issue-0080: Typed value of Document, PI and Comment nodes].

If the node (or node kind) has no typed value, the empty sequence is returned.

4.1.7 type Accessor

The dm:type accessor returns a sequence containing zero or one xs:QName.

For element nodes, dm:type returns the globally declared QName of the type of the node or xs:anyType if it is locally declared or no type information exists.

For attribute nodes, dm:type returns the globally declared QName of the type of the node or xs:anySimpleType if it is locally declared or no type information exists.

For other node kinds, it always returns the empty sequence.

4.1.8 children Accessor

The dm:children accessor returns a sequence containing zero or more nodes.

For document and element nodes, it returns the nodes that are the children of that node. It returns the empty sequence for document and element nodes that have no children.

For all other nodes, it always returns the empty sequence.

A document node or an element node is the parent of each of its child nodes. Nodes never share children: if two nodes have distinct identities, then no child of one node will be a child of the other node.

4.1.9 attributes Accessor

The dm:attributes accessor returns a sequence containing zero or more attribute nodes.

For element nodes, these are the attributes of the node. For all other nodes, it always returns the empty sequence.

4.1.10 namespaces Accessor

The dm:namespaces accessor returns a sequence containing zero or more namespace nodes.

For element nodes, these are the namespaces of the node. For all other nodes, it always returns the empty sequence.

4.2.1 Overview

Document nodes encapsulate XML documents. Documents have the following properties:

• base-uri, possibly empty.

• children

Document nodes must satisfy the following constraints.

1. An document node's children may not contain two consecutive text nodes. Consecutive text nodes are collapsed by the document constructor into one text node.

2. If a node N is a child of a document D, then the parent of N must be D.

3. If a node N has a parent document D, then N must be among the children of D.

4. Every child of a document must be distinct.

In a well-formed document, the children of the document node consist exclusively of element nodes, processing-instruction nodes, and comment nodes, and exactly one of these children is an element node. A document node in the data model is more permissive: it allows more than one element node as a child and also permits text nodes as children. See [Issue-0074: Do we need Document fragments].

4.2.2 Constructor

A document node can be constructed using dm:document-node which returns a new node with unique identity, distinct from all other nodes.

The constructor takes an optional base URI value and a non-empty sequence of children nodes as arguments.

The sequence of nodes passed as $children must not be empty and must consist only of element, processing instruction, comment, and text nodes. See [Issue-0090: Documents can be empty].

If consecutive text nodes are specified as the children of a document node they are collapsed into one text node whose string value is the concatenation of the string values of the consecutive text nodes.

4.2.3 Accessors

Two additional accessors are defined on document nodes:

The dm:unparsed-entity-system-id accessor returns the system identifier of an unparsed external entity declared in the specified document. If no entity with the name specified in $entityname exists, or if the entity is not an external unparsed entity, the empty sequence is returned.

The dm:unparsed-entity-public-id accessor returns the public identifier of an unparsed external entity declared in the specified document. If no entity with the name specified in $entityname exists, or if the entity is not an external unparsed entity, or if the entity has no public identifier, the empty sequence is returned.

4.2.4 PSVI to Datamodel Mapping

When a data model fragment is created from the PSVI, a document information item is mapped to a Document Node. The precise transformation is described by specifying the PSVI property corresponding to each argument of the document node constructor:

To construct the value of the $children argument, for each element, processing instruction, comment, and maximal sequence of adjacent characater information items found in the [children] property, a corresponding Element, Processing Instruction, Comment, and Text node is constructed and that sequence of nodes is used as the value. If present among the [children], the [document type declaration] information item is ignored.

4.2.5 Data Model to Infoset Mapping

The mapping of the data model to the XML Information Set maps a Document Node to a document information item. The properties of the document information item are constructed as follows:

4.3.1 Overview

Element nodes encapsulate XML elements. Elements have the following properties:

• base-uri, possibly empty.

• node-name

• parent

• type, possibly empty

• children, possibly empty

• attributes, possibly empty

• namespaces, possibly empty

Element nodes must satisfy the following constraints.

1. An element node's children may not contain two consecutive text nodes. Consecutive text nodes are collapsed by the element constructor into one text node.

2. If a node N is a child of an element E, then the parent of N must be E.

3. If a node N has a parent element E, then N must be among the children of E.

4. Every child of an element must be distinct.

5. The attributes of an element must have distinct names.

6. The namespace nodes of an element must have distinct names. At most one of the namespace nodes of an element has no name (this is the default namespace). A namespace node whose namespace URI is the zero-length string must have no name. No namespace node may have the name "xmlns".

The element node constructor assures that the first three constraints are satisfied.

4.3.2 Constructor

An element node can be constructed using dm:element-node which returns a new node with unique identity, distinct from all other nodes.

The constructor takes an expanded-QName, a sequence of namespace nodes, a sequence of attribute nodes, a sequence of child nodes, the node's type, and an optional base URI as arguments.

The sequence of nodes passed as $children must consist only of element, processing instruction, comment, and text nodes.

If consecutive text nodes are specified as the children of an element node they are collapsed into one text node whose string value is the concatenation of the string values of the consecutive text nodes.

To guarantee that the parent-child relationship is invertible, (i.e. that the parent of any child of a node is itself and that any node that has a parent is among its parent's children), the element constructors logically create a copy of all of their namespace, attribute, and children arguments and set the parent property of these nodes to the newly created element node. As long as the parent-child constraint is satisfied, an implementation of the data model may choose to use specialized techniques to avoid creating physical copies of the arguments to an element constructor. See [Issue-0052: Element constructor copies nodes?].

The data model permits element nodes without parents. In fact element nodes created by the element node constructor never have parents unless they are enclosed in other node constructors. Such nodes may represent partial results during expression processing.

4.3.3 Accessors

The dm:base-uri accessor returns the base-uri property of the element node, if it exists. If it does not exist, the base URI of the element's parent is returned. In other words, the value returned must be the same as the value of dm:base-uri(dm:parent()) although implemetations are not required to implement it in that way.

The accessors dm:namespaces and dm:attributes return the same set of namespace and attribute nodes (respectively) that were supplied to the constructor, but they are not constrained to return them in the same order. See [Issue-0086: Nodes returned by namespaces and attributes]

The dm:parent accessor returns the empty sequence if the element has no parent.

If the element node's type is xs:anyType, the dm:typed-value accessor returns the node's string value as xs:anySimpleType. If the type is a complex type with complex content, invoking dm:typed-value raises an error.

The dm:typed-value accessor returns the typed-value of the node, which is a sequence of zero or more atomic values. The typed-value is closely related to the node's string-value and its type. For instance when the node's string-value is "3.14" and its type is xs:decimal, the typed-value is a sequence containing the atomic value 3.14 of type decimal. In fact, when the type is an atomic type, typed-value is always the atomic-value constructed from the string-value and the type.

In the general case, dm:typed-value constructs a sequence of atomic values. These values are derived from the string-value of the element and its type, in such a way as to be consistent with validation.

4.3.4 PSVI to Data Model Mapping

When a data model fragment is created from the PSVI, an element information item is mapped to an Element Node. The precise transformation is described by specifying the PSVI property corresponding to each argument of the element node constructor.

$qname

An xs:QName constructed from the [local name] property and the [namespace name] property

$nsnodes

A set of Namespace Nodes constructed from the namespace information items appearing in the [in-scope namespaces] property.

Implementations may provide mechanisms to allow some or all of the namespaces in the [in-scope namespaces] property to be discarded from the data model.

$attrnodes

A set of Attribute Nodes constructed from the attribute information items appearing in the [attributes] property. This includes all of the "special" attributes (xml:lang, xml:space, xsi:type, etc.) but does not include namespace declarations (because they are not attributes).

The special nature of xsi:nil is still being discussed, see [Issue-0071: Magic Attributes].

$children

• If the [schema normalized value] PSVI property exists, a single text node whose string value is the value of that property.

• Otherwise, the sequence of nodes constructed in the following way from the information items found in the [children] property: for each element, processing instruction, comment, and maximal sequence of adjacent characater information items found in the [children] property, a corresponding Element, Processing Instruction, Comment, and Text node is constructed.

  Because the data model requires that all general entities be expanded, there will never be unexpanded entity reference information item children.

$type

The xs:QName computed as described in 3.6 Mapping PSV Infoset additions to Types. Note that if the type referenced would be a union type then type refers to the member type that actually validated the schema normalized value.

The unique ID of the element node is an identifier optionally assigned by the user. It corresponds to the [normalized value] property of the attribute information item in the [attributes] property that has a type ID, if one exists.

4.3.5 Data Model to Infoset Mapping

The mapping of the data model to the XML Information Set maps an Element Node to an element information item. The properties of the element information item are constructed as follows:

An implementation must construct the value of the [prefix] property as if the following algorithm was applied: if the element has at least one namespace node whose namespace URI is the same as the namespace name of the QName returned by the dm:node-name accessor, it returns the local part of the name of that namespace node or the empty string if the namespace node has no name. If there are several such namespace nodes, it chooses one of them arbitrarily. If there is no such namespace node, it generates an arbitrary prefix that is distinct from the dm:node-name of any of the element's namespaces.

If a new prefix is generated, a corresponding namespace information item must be added to the [in-scope namespaces] property of the element information item. The namespace information item must associate the generated prefix with the namespace name of the QName returned by the element's dm:node-name accessor.

4.4.1 Overview

Attribute nodes encapsulate XML attributes. Attributes have the following properties:

• node-name

• parent

• type, possibly empty

The above information associated with an attribute node is set during construction and can be accessed later via the accessor functions.

For convenience, the element node that owns this attribute is called its "parent" even though an attribute node is not a "child" of its parent element.

4.4.2 Constructor

An attribute node can be constructed using dm:attribute-node which returns a new node with unique identity, distinct from all other nodes.

The constructor takes the attribute's expanded-QName, string value, and type.

Like all other node constructors, the attribute node constructor has the effect of creating a new node with a unique identity, distinct from all other nodes.

4.4.3 Accessors

4.4.4 PSVI to Data Model Mapping

When a data model fragment is created from the PSVI an attribute information item is mapped to an Attribute Node. The precise transformation is described by specifying the PSVI property corresponding to each argument of the attribute node constructor.

$qname

An xs:QName constructed from the [local name] property and the [namespace name] property

$value

• The [schema normalized value] PSVI property if that exists, or

• the [normalized value] property.

$type

The xs:QName computed as described in 3.6 Mapping PSV Infoset additions to Types. Note that if the type referenced would be a union type then type refers to the member type that actually validated the schema normalized value.

4.4.5 Data Model to Infoset Mapping

The mapping of the data model to the XML Information Set maps an Attribute Node to an attribute information item. The properties of the corresponding attribute information item are constructed as follows:

If the attribute node has a parent, an implementation must construct the value of the [prefix] property in the following way: if the attribute has a parent, in the same way that a prefix would be constructed for that element, otherwise a prefix is chosen arbitrarily, and no attempt is made to associate the prefix with the namespace URI.

4.5.1 Overview

Namespace nodes encapsulate XML namespaces. Namespaces have the following properties:

• prefix, possibly empty.

• uri

In XPath 1.0, namespace nodes were directly accessible by applications, by means of the namespace axis. In XPath 2.0 the namespace axis is deprecated, and it is not available at all in XQuery 1.0. XPath 2.0 implementations are not required to expose the namespace axis, though they may do so if they wish to offer backwards compatibility. The information held in namespace nodes is instead made available to applications using two functions defined in [Functions and Operators], namely xf:get-in-scope-namespaces and xf:get-namespace-uri-for-prefix. Certain properties of namespace nodes are not exposed by these functions: in particular, properties related to the identity of namespace nodes, their parentage, and their position in document order. Implementations that do not expose the namespace axis can therefore avoid the overhead of maintaining this information.

The above information associated with a namespace node is set during construction and can be accessed later via the accessor functions.

Each element node has an associated set of namespace nodes corresponding to its in-scope namespaces, and that element node acts as the parent of those namespace nodes.

4.5.2 Constructor

A namespace node can be constructed using dm:namespace-node which returns a new node with unique identity, distinct from all other nodes.

The constructor takes a namespace prefix and the URI of the namespace being declared.

The namespace prefix may be the empty sequence. If the URI is the zero-length string, the prefix must be the empty sequence.

4.5.3 Accessors

4.5.4 PSVI to Data Model Mapping

When a data model fragment is created from the PSVI a namespace information item is mapped to a Namespace Node. The precise transformation is described by specifying the PSVI property corresponding to each argument of the attribute node constructor.

$prefix

The [prefix] property.

$uri

The [namespace name] property.

4.5.5 Data Model to Infoset Mapping

The mapping of the data model to the XML Information Set maps a Namespace Node to a namespace information item. The properties of the namespace information item are constructed as follows:

4.6.1 Overview

Processing instruction nodes encapsulate XML processing instructions. Processing instructions have the following properties:

• target

• content

• parent, possibly empty

4.6.2 Constructor

A processing instructoin node can be constructed using dm:processing-instruction-node which returns a new node with unique identity, distinct from all other nodes.

The constructor takes an NCName, a string, and an optional base URI.

The string '?>' may not occur within a processing instruction's target or content value ([XML Recommendation]).

4.6.3 Accessors

4.6.4 PSVI to Data Model Mapping

When a data model fragment is created from the PSVI, a processing instruction information item is mapped to a Processing Instruction Node. The precise transformation is described by specifying the PSVI property corresponding to each argument of the processing instruction node constructor.

$target

The value of the [target] property.

$content

The value of the [content] property.

$base-uri

The value of the [base URI] property.

There are no processing instruction nodes for processing instructions that are children of a document type declaration information item.

4.6.5 Data Model to Infoset Mapping

The mapping of the data model to the XML Information Set maps a Processing Instruction Node to a processing instruction information item. The properties of the processing instruction information item are constructed as follows:

4.7.1 Overview

Comment nodes encapsulate XML comments. Comments have the following properties:

• the content

• parent

4.7.2 Constructor

A comment node can be constructed using dm:comment-node which returns a new node with unique identity, distinct from all other nodes.

The constructor takes a string value.

The string "--" (two consecutive hyphens) must not occur within a comment's string value ([XML Recommendation]).

4.7.3 Accessors

4.7.4 PSVI to Data Model Mapping

When a data model fragment is created from the PSVI a comment information item is mapped to a Comment Node. The precise transformation is described by specifying the PSVI property corresponding to each argument of the comment node constructor.

$content

The value of the [content] property.

There are no comment nodes for comments that are children of a document type declaration information item.

4.7.5 Data Model to Infoset Mapping

The mapping of the data model to the XML Information Set maps a Comment Node to a comment information item. The properties of the corresponding comment information item are constructed as follows:

4.8.1 Overview

Text nodes encapsulate XML character content. Text has the following properties:

• content

• parent

Text nodes must satisfy the following constraint:

1. A text node cannot contain the empty string as its content.

In addition, document and element nodes impose the constraint that two consecutive text nodes can never occur as adjacent siblings.

4.8.2 Constructor

A text node can be constructed using dm:text-node which returns a new node with unique identity, distinct from all other nodes.

The constructor takes a string value.

4.8.3 Accessors

4.8.4 PSVI to Data Model Mapping

When a data model fragment is created from the PSVI a maximal sequence of consecutive character information items are mapped to a Text Node. The precise transformation is described by specifying the PSVI property corresponding to the argument of the comment node constructor.

$content

A string comprised of characters that correspond to the [character code] properties of each of the character information items.

4.8.5 Data Model to Infoset Mapping

The mapping of the data model to the XML Information Set maps a Text Node to a sequence of character information items. The properties of the corresponding character information items are constructed as follows: