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1. Document Object Model XPath

Editor:: Ray Whitmer, Netscape/AOL

1.1. Introduction
1.2. Mapping DOM to XPath
1.3. Interfaces
- XPathException, XPathExceptionCode, XPathEvaluator, XPathExpression, XPathNSResolver, XPathResult, XPathSetIterator, XPathSetSnapshot, XPathNamespace

1.1. Introduction

XPath 1.0 [XPath 1.0] is becoming an important part of a variety of many specifications including XForms, XPointer, XSL, XML Query, and so on. It is also a clear advantage for user applications which use DOM to be able to use XPath expressions to locate nodes automatically and declaratively. But liveness issues have plagued each attempt to get a list of DOM nodes matching specific criteria, as would be expected for an XPath API. There have also traditionally been model mismatches between DOM and XPath. This proposal specifies new interfaces and approaches to resolving these issues.

1.2. Mapping DOM to XPath

This section considers the differences between the Document Object Model [DOM Level 3 Core] and the XPath 1.0 model [XPath 1.0].

1.2.1. Text Nodes

The XPath model relies on the XML Information Set [XML Information set] ands represents Character Information Items in a single logical text node where DOM may have multiple fragmented Text nodes due to cdata sections, entity references, etc. Instead of returning multiple nodes where XPath sees a single logical text node, only the first non-empty DOM Text or CDATASection node of any logical XPath text will be returned in the node set. Applications using XPath in an environment with fragmented text nodes must manually gather the text of a single logical text node possibly from multiple nodes beginning with the first Text node or CDATASection node returned by the implementation.

Note: In an attempt to better implement the XML Information Set, DOM Level 3 Core [DOM Level 3 Core] adds the attribute wholeText on the Text interface for retrieving the whole text for logically-adjacent Text nodes and the method replaceWholeText for replacing those nodes.

1.2.2. Namespace Nodes

The XPath model expects namespace nodes for each in-scope namespace to be attached to each element. DOM and certain other W3C Information Set conformant implementations only maintain the declaration of namespaces instead of replicating them on each Element where they are in-scope. The DOM implementation of XPath returns a new node of type XPATH_NAMESPACE_NODE, defined in the XPathNamespace interface, to properly preserve identity and ordering. This node type is only visible using the XPath evaluation methods.

1.2.3. Document order

The document order of nodes in the DOM Core has been defined to be compatible with the XPath document order. The XPath DOM is extending the document order of the DOM Core to include the XPathNamespace nodes. Element nodes occur before their children. The attribute nodes and namespace nodes of an element occur before the children of the element. The namespace nodes are defined to occur before the attribute nodes. The relative order of namespace nodes is implementation-dependent. The relative order of attribute nodes is implementation-dependent. The compareTreePosition method on the Node interface defined in the DOM Core must compare the XPathNamespace nodes using this extending document order if the XPath DOM module is supported.

1.3. Interfaces

A DOM application may use the hasFeature(feature, version) method of the DOMImplementation interface with parameter values "XPath" and "3.0" (respectively) to determine whether or not the event module is supported by the implementation. In order to fully support this module, an implementation must also support the "Core" feature defined in the DOM Level 3 Core specification [DOM Level 3 Core]. Please, refer to additional information about conformance in the DOM Level 3 Core specification [DOM Level 3 Core].

Exception XPathException

A new exception has been created for exceptions specific to these XPath interfaces.

IDL Definition

exception XPathException {
  unsigned short   code;
};
// XPathExceptionCode
const unsigned short      INVALID_EXPRESSION_ERR         = 1;
const unsigned short      TYPE_ERR                       = 2;

Definition group XPathExceptionCode

Defined Constants

INVALID_EXPRESSION_ERR: If the expression is not a legal expression according to the rules of the specific XPathEvaluator. If the XPathEvaluator was obtained by casting the document, the expression must be XPath 1.0 with no special extension functions.
TYPE_ERR: If the expression cannot be converted to return the specified type.

Interface XPathEvaluator

The evaluation of XPath expressions is provided by XPathEvaluator, which will provide evaluation of XPath 1.0 expressions with no specialized extension functions or variables. It is expected that the XPathEvaluator interface will be implemented on the same object which implements the Document interface in an implementation which supports the XPath DOM module. XPathEvaluator implementations may be available from other sources that may provide support for new versions of XPath or special extension functions or variables which are not defined in this specification.

IDL Definition

interface XPathEvaluator {
  XPathExpression    createExpression(in DOMString expression, 
                                      in XPathNSResolver resolver)
                                        raises(XPathException, 
                                               DOMException);
  XPathResult        createResult();
  XPathNSResolver    createNSResolver(in Node nodeResolver);
  XPathResult        evaluate(in DOMString expression, 
                              in Node contextNode, 
                              in XPathNSResolver resolver, 
                              in unsigned short type, 
                              in XPathResult result)
                                        raises(XPathException, 
                                               DOMException);
};

Methods

createExpression

Creates a parsed XPath expression with resolved namespaces. This is useful when an expression will be reused in an application since it makes it possible to compile the expression string into a more efficient internal form and preresolve all namespace prefixes which occur within the expression.

Parameters

expression of type DOMString: The XPath expression string to be parsed.
resolver of type XPathNSResolver: The resolver permits translation of prefixes within the XPath expression into appropriate namespace URIs. If this is specified as null, any namespace prefix within the expression will result in DOMException being thrown with the code NAMESPACE_ERR.

Return Value

XPathExpression

The compiled form of the XPath expression.

Exceptions

`XPathException`	INVALID_EXPRESSION_ERR: Raised if the expression is not legal according to the rules of the `XPathEvaluator`i
`DOMException`	NAMESPACE_ERR: Raised if the expression contains namespace prefixes which cannot be resolved by the specified `XPathNSResolver`.

createNSResolver

Adapts any DOM node to resolve namespaces so that an XPath expression can be easily evaluated relative to the context of the node where it appeared within the document. This adapter works by calling the method lookupNamespacePrefix on Node.

Parameters

nodeResolver of type Node: The node to be used as a context for namespace resolution.

Return Value

XPathNSResolver

XPathNSResolver which resolves namespaces with respect to the definitions in scope for a specified node.

No Exceptions

createResult

Creates an XPathResult object which may be passed as a parameter to the evaluation methods of this XPathEvaluator so that a new one is not created on each call to an evaluation method.

Return Value

XPathResult

An empty XPathEvaluator with type ANY_TYPE.

No Parameters

No Exceptions

evaluate

Evaluates an XPath expression string and returns a result of the specified type if possible.

Parameters

expression of type DOMString: The XPath expression string to be parsed and evaluated.
contextNode of type Node: The context is context node for the evaluation of this XPath expression. If the XPathEvaluator was obtained by casting the Document then this must be owned by the same document and must be a Document, Element, Attribute, Text, CDATASection, Comment, ProcessingInstruction, or XPathNamespace node. If the context node is a Text or a CDATASection, then the context is interpreted as the whole logical text node as seen by XPath, unless the node is empty in which case it may not serve as the XPath context.
resolver of type XPathNSResolver: The resolver permits translation of prefixes within the XPath expression into appropriate namespace URIs. If this is specified as null, any namespace prefix within the expression will result in DOMException being thrown with the code NAMESPACE_ERR.
type of type unsigned short: If a specific type is specified, then the result will be coerced to return the specified type relying on XPath conversions and fail if the desired coercion is not possible. This must be one of the type codes of XPathResult.
result of type XPathResult: The result specifies a specific XPathResult to be reused and returned by this method. If this is specified as null, a new XPathResult will be constructed and returned. Any XPathResult which was not created by this XPathEvaluator may be ignored as though a null were passed as the parameter.

Return Value

XPathResult

The result of the evaluation of the XPath expression.

Exceptions

XPathException

INVALID_EXPRESSION_ERR: Raised if the expression is not legal according to the rules of the XPathEvaluatori

TYPE_ERR: Raised if the result cannot be converted to return the specified type.

DOMException

NAMESPACE_ERR: Raised if the expression contains namespace prefixes which cannot be resolved by the specified XPathNSResolver.

WRONG_DOCUMENT_ERR: The Node is from a document that is not supported by this XPathEvaluator.

NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath context node.

Interface XPathExpression

The XPathExpression interface represents a parsed and resolved XPath expression.

IDL Definition

interface XPathExpression {
  XPathResult        evaluate(in Node contextNode, 
                              in unsigned short type, 
                              in XPathResult result)
                                        raises(XPathException, 
                                               DOMException);
};

Methods

evaluate

Evaluates this XPath expression and returns a result.

Parameters

contextNode of type Node: The context is context node for the evaluation of this XPath expression.
If the XPathEvaluator was obtained by casting the Document then this must be owned by the same document and must be a Document, Element, Attribute, Text, CDATASection, Comment, ProcessingInstruction, or XPathNamespace node.
If the context node is a Text or a CDATASection, then the context is interpreted as the whole logical text node as seen by XPath, unless the node is empty in which case it may not serve as the XPath context.
type of type unsigned short: If a specific type is specified, then the result will be coerced to return the specified type relying on XPath conversions and fail if the desired coercion is not possible. This must be one of the type codes of XPathResult.
result of type XPathResult: The result specifies a specific XPathResult to be reused and returned by this method. If this is specified as null, a new XPathResult will be constructed and returned. Any XPathResult which was not created by this XPathEvaluator may be ignored as though a null were passed as the parameter.

Return Value

XPathResult

The result of the evaluation of the XPath expression.

Exceptions

XPathException

TYPE_ERR: Raised if the result cannot be converted to return the specified type.

DOMException

WRONG_DOCUMENT_ERR: The Node is from a document that is not supported by the XPathExpression that created this XPathExpression.

NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath context node.

Interface XPathNSResolver

The XPathNSResolver interface permit prefix strings in the expression to be properly bound to namespaceURI strings. XPathEvaluator can construct an implementation of XPathNSResolver from a node, or the interface may be implemented by any application.

IDL Definition

interface XPathNSResolver {
  DOMString          lookupNamespaceURI(in DOMString prefix);
};

Methods

lookupNamespaceURI

Look up the namespace URI associated to the given namespace prefix. The XPath evaluator must never call this with a null or empty argument, because the result of doing this is undefined.

Parameters

prefix of type DOMString: The prefix to look for.

Return Value

DOMString

Returns the associated namespace URI or null if none is found.

No Exceptions

Interface XPathResult

The XPathResult interface represents the result of the evaluation of an XPath expression within the context of a particular node. Since evaluation of an XPath expression can result in various result types, this object makes it possible to discover and manipulate the type and value of the result.

IDL Definition

interface XPathResult {

  // XPathResultType
  const unsigned short      ANY_TYPE                       = 0;
  const unsigned short      NUMBER_TYPE                    = 1;
  const unsigned short      STRING_TYPE                    = 2;
  const unsigned short      BOOLEAN_TYPE                   = 3;
  const unsigned short      NODE_SET_TYPE                  = 4;
  const unsigned short      SINGLE_NODE_TYPE               = 5;

  readonly attribute unsigned short  resultType;
  readonly attribute double          numberValue;
                                        // raises(XPathException) on retrieval

  readonly attribute DOMString       stringValue;
                                        // raises(XPathException) on retrieval

  readonly attribute boolean         booleanValue;
                                        // raises(XPathException) on retrieval

  readonly attribute Node            singleNodeValue;
                                        // raises(XPathException) on retrieval

  XPathSetIterator   getSetIterator(in boolean ordered)
                                        raises(XPathException, 
                                               DOMException);
  XPathSetSnapshot   getSetSnapshot(in boolean ordered)
                                        raises(XPathException, 
                                               DOMException);
};

Definition group XPathResultType

An integer indicating what type of result this is.

Defined Constants

ANY_TYPE: This code does not represent a specific type. An evaluation of an XPath expression will never produce this type. If this type is requested, then the evaluation must return whatever type naturally results from evaluation of the expression.
BOOLEAN_TYPE: The result is a boolean as defined by XPath 1.0.
NODE_SET_TYPE: The result is a node set as defined by XPath 1.0.
NUMBER_TYPE: The result is a number as defined by XPath 1.0.
SINGLE_NODE_TYPE: The result is a single node, which may be any node of the node set defined by XPath 1.0, or null if the node set is empty. This is a convenience that permits optimization where the caller knows that no more than one such node exists because evaluation can stop after finding the one node of an expression that would otherwise return a node set (of type NODE_SET_TYPE).
Where it is possible that multiple nodes may exist and the first node in document order is required, a NODE_SET_TYPE should be processed using an ordered iterator, because there is no order guarantee for a single node.
STRING_TYPE: The result is a string as defined by XPath 1.0.

Attributes

booleanValue of type boolean, readonly

The value of this boolean result.

Exceptions on retrieval

XPathException

TYPE_ERR: raised if resultType is not BOOLEAN_TYPE.

numberValue of type double, readonly

The value of this number result.

Exceptions on retrieval

XPathException

TYPE_ERR: raised if resultType is not NUMBER_TYPE.

resultType of type unsigned short, readonly

A code representing the type of this result, as defined by the type constants.

singleNodeValue of type Node, readonly

The value of this single node result, which may be null. This result is not guaranteed to be the first node in document order where the expression evaluates to multiple nodes.

Exceptions on retrieval

XPathException

TYPE_ERR: raised if resultType is not SINGLE_NODE_TYPE.

stringValue of type DOMString, readonly

The value of this string result.

Exceptions on retrieval

XPathException

TYPE_ERR: raised if resultType is not STRING_TYPE.

Methods

getSetIterator

Creates an XPathSetIterator which may be used to iterate over the nodes of the set of this result.

Parameters

ordered of type boolean: The set must be iterated in document order.

Return Value

XPathSetIterator

An XPathSetIterator which may be used to iterate the node set.

Exceptions

`XPathException`	TYPE_ERR: raised if `resultType` is not `NODE_SET_TYPE`.
`DOMException`	INVALID_STATE_ERR: The document has been mutated since the result was returned.

getSetSnapshot

Creates an XPathSetSnapshot which lists the nodes of the set of this result. Unlike an iterator, after the snapshot has been requested, document mutation does not invalidate it.

Parameters

ordered of type boolean: The set must be listed in document order.

Return Value

XPathSetSnapshot

An XPathSetSnapshot which may be used to list the node set.

Exceptions

`XPathException`	TYPE_ERR: raised if `resultType` is not NODE_SET_TYPE.
`DOMException`	INVALID_STATE_ERR: The document has been mutated since the result was returned.

Interface XPathSetIterator

The XPathSetIterator interface iterates the node set resulting from evaluation of an XPath expression.

IDL Definition

interface XPathSetIterator {
  Node               nextNode()
                                        raises(DOMException);
};

Methods

nextNode

Returns the next node from the XPathResult node set. If there are no more nodes in the set to be returned by the iterator, this method returns null.

Return Value

Node

Returns the next node.

Exceptions

DOMException

INVALID_STATE_ERR: The document has been mutated since the node set result was returned.

No Parameters

Interface XPathSetSnapshot

The XPathSetSnapshot interface lists the node set resulting from an evaluation of an XPath expression as a static list that is not invalidated or changed by document mutation.

The individual nodes of a XPathSetSnapshot may be manipulated in the hierarchy and these changes are seen immediately by users referencing the nodes through the snapshot.

IDL Definition

interface XPathSetSnapshot {
  Node               item(in unsigned long index);
  readonly attribute unsigned long   length;
};

Attributes

length of type unsigned long, readonly: The number of nodes in the list. The range of valid child node indices is 0 to length-1 inclusive.

Methods

item

Returns the indexth item in the collection. If index is greater than or equal to the number of nodes in the list, this method returns null.

Parameters

index of type unsigned long: Index into the collection.

Return Value

Node

The node at the indexth position in the NodeList, or null if that is not a valid index.

No Exceptions

Interface XPathNamespace

The XPathNamespace interface is returned by XPathResult interfaces to represent the XPath namespace node type that DOM lacks. There is no public constructor for this node type. Attempts to place it into a hierarchy or a NamedNodeMap result in a DOMException with the code HIERARCHY_REQUEST_ERR. This node is read only, so methods or setting of attributes that would mutate the node result in a DOMException with the code NO_MODIFICATION_ALLOWED_ERR.

The core specification describes attributes of the Node interface that are different for different node node types but does not describe XPATH_NAMESPACE_NODE, so here is a description of those attributes for this node type. All attributes of Node not described in this section have a null or false value.

ownerDocument matches the ownerDocument of the ownerElement even if the element is later adopted.

prefix is the prefix of the namespace represented by the node.

NodeName is the same as prefix.

NodeType is equal to XPATH_NAMESPACE_NODE.

namespaceURI is the namespace URI of the namespace represented by the node.

adoptNode, cloneNode, and importNode fail on this node type by raising a DOMException with the code NOT_SUPPORTED_ERR.

IDL Definition

interface XPathNamespace : Node {

  // XPathNodeType
  const unsigned short      XPATH_NAMESPACE_NODE           = 13;

  readonly attribute Element         ownerElement;
};

Definition group XPathNodeType

An integer indicating which type of node this is.

Note: There is currently only one type of node which is specific to XPath. The numbers in this list must not collide with the values assigned to core node types.

Defined Constants

XPATH_NAMESPACE_NODE: The node is a Namespace.

Attributes

ownerElement of type Element, readonly: The Element on which the namespace was in scope when it was requested. This does not change on a returned namespace node even if the document changes such that the namespace goes out of scope on that element and this node is no longer found there by XPath.

Appendix A: IDL Definitions

This appendix contains the complete OMG IDL [OMGIDL] for the Level 3 Document Object Model XPath definitions.

The IDL files are also available as: http://www.w3.org/TR/2001/WD-DOM-Level-3-XPath-20011031/idl.zip

xpath.idl:

// File: xpath.idl

#ifndef _XPATH_IDL_
#define _XPATH_IDL_

#include "dom.idl"

#pragma prefix "dom.w3c.org"
module xpath
{

  typedef dom::DOMString DOMString;
  typedef dom::Node Node;
  typedef dom::Element Element;

  interface XPathNSResolver;
  interface XPathResult;
  interface XPathExpression;
  interface XPathSetIterator;
  interface XPathSetSnapshot;

  exception XPathException {
    unsigned short   code;
  };
  // XPathExceptionCode
  const unsigned short      INVALID_EXPRESSION_ERR         = 1;
  const unsigned short      TYPE_ERR                       = 2;


  interface XPathEvaluator {
    XPathExpression    createExpression(in DOMString expression, 
                                        in XPathNSResolver resolver)
                                        raises(XPathException, 
                                               dom::DOMException);
    XPathResult        createResult();
    XPathNSResolver    createNSResolver(in Node nodeResolver);
    XPathResult        evaluate(in DOMString expression, 
                                in Node contextNode, 
                                in XPathNSResolver resolver, 
                                in unsigned short type, 
                                in XPathResult result)
                                        raises(XPathException, 
                                               dom::DOMException);
  };

  interface XPathExpression {
    XPathResult        evaluate(in Node contextNode, 
                                in unsigned short type, 
                                in XPathResult result)
                                        raises(XPathException, 
                                               dom::DOMException);
  };

  interface XPathNSResolver {
    DOMString          lookupNamespaceURI(in DOMString prefix);
  };

  interface XPathResult {

    // XPathResultType
    const unsigned short      ANY_TYPE                       = 0;
    const unsigned short      NUMBER_TYPE                    = 1;
    const unsigned short      STRING_TYPE                    = 2;
    const unsigned short      BOOLEAN_TYPE                   = 3;
    const unsigned short      NODE_SET_TYPE                  = 4;
    const unsigned short      SINGLE_NODE_TYPE               = 5;

    readonly attribute unsigned short  resultType;
    readonly attribute double          numberValue;
                                        // raises(XPathException) on retrieval

    readonly attribute DOMString       stringValue;
                                        // raises(XPathException) on retrieval

    readonly attribute boolean         booleanValue;
                                        // raises(XPathException) on retrieval

    readonly attribute Node            singleNodeValue;
                                        // raises(XPathException) on retrieval

    XPathSetIterator   getSetIterator(in boolean ordered)
                                        raises(XPathException, 
                                               dom::DOMException);
    XPathSetSnapshot   getSetSnapshot(in boolean ordered)
                                        raises(XPathException, 
                                               dom::DOMException);
  };

  interface XPathSetIterator {
    Node               nextNode()
                                        raises(dom::DOMException);
  };

  interface XPathSetSnapshot {
    Node               item(in unsigned long index);
    readonly attribute unsigned long   length;
  };

  interface XPathNamespace : Node {

    // XPathNodeType
    const unsigned short      XPATH_NAMESPACE_NODE           = 13;

    readonly attribute Element         ownerElement;
  };
};

#endif // _XPATH_IDL_

Appendix B: Java Language Binding

This appendix contains the complete Java [Java] bindings for the Level 3 Document Object Model XPath.

The Java files are also available as http://www.w3.org/TR/2001/WD-DOM-Level-3-XPath-20011031/java-binding.zip

B.1: Other XPath interfaces

org/w3c/dom/xpath/XPathException.java:

package org.w3c.dom.xpath;

public class XPathException extends RuntimeException {
    public XPathException(short code, String message) {
       super(message);
       this.code = code;
    }
    public short   code;
    // XPathExceptionCode
    public static final short INVALID_EXPRESSION_ERR    = 1;
    public static final short TYPE_ERR                  = 2;

}

org/w3c/dom/xpath/XPathEvaluator.java:

package org.w3c.dom.xpath;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

public interface XPathEvaluator {
    public XPathExpression createExpression(String expression, 
                                            XPathNSResolver resolver)
                                            throws XPathException, DOMException;

    public XPathResult createResult();

    public XPathNSResolver createNSResolver(Node nodeResolver);

    public XPathResult evaluate(String expression, 
                                Node contextNode, 
                                XPathNSResolver resolver, 
                                short type, 
                                XPathResult result)
                                throws XPathException, DOMException;

}

org/w3c/dom/xpath/XPathExpression.java:

package org.w3c.dom.xpath;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

public interface XPathExpression {
    public XPathResult evaluate(Node contextNode, 
                                short type, 
                                XPathResult result)
                                throws XPathException, DOMException;

}

org/w3c/dom/xpath/XPathNSResolver.java:

package org.w3c.dom.xpath;

public interface XPathNSResolver {
    public String lookupNamespaceURI(String prefix);

}

org/w3c/dom/xpath/XPathResult.java:

package org.w3c.dom.xpath;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

public interface XPathResult {
    // XPathResultType
    public static final short ANY_TYPE                  = 0;
    public static final short NUMBER_TYPE               = 1;
    public static final short STRING_TYPE               = 2;
    public static final short BOOLEAN_TYPE              = 3;
    public static final short NODE_SET_TYPE             = 4;
    public static final short SINGLE_NODE_TYPE          = 5;

    public short getResultType();

    public double getNumberValue()
                                     throws XPathException;

    public String getStringValue()
                                     throws XPathException;

    public boolean getBooleanValue()
                                     throws XPathException;

    public Node getSingleNodeValue()
                                     throws XPathException;

    public XPathSetIterator getSetIterator(boolean ordered)
                                           throws XPathException, DOMException;

    public XPathSetSnapshot getSetSnapshot(boolean ordered)
                                           throws XPathException, DOMException;

}

org/w3c/dom/xpath/XPathSetIterator.java:

package org.w3c.dom.xpath;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

public interface XPathSetIterator {
    public Node nextNode()
                         throws DOMException;

}

org/w3c/dom/xpath/XPathSetSnapshot.java:

package org.w3c.dom.xpath;

import org.w3c.dom.Node;

public interface XPathSetSnapshot {
    public Node item(int index);

    public int getLength();

}

org/w3c/dom/xpath/XPathNamespace.java:

package org.w3c.dom.xpath;

import org.w3c.dom.Element;
import org.w3c.dom.Node;

public interface XPathNamespace extends Node {
    // XPathNodeType
    public static final short XPATH_NAMESPACE_NODE      = 13;

    public Element getOwnerElement();

}

Appendix C: ECMAScript Language Binding

This appendix contains the complete ECMAScript [ECMAScript] binding for the Level 3 Document Object Model XPath definitions.

Prototype Object XPathException

The XPathException class has the following constants:

XPathException.INVALID_EXPRESSION_ERR: This constant is of type Number and its value is 1.
XPathException.TYPE_ERR: This constant is of type Number and its value is 2.

Object XPathException

The XPathException object has the following properties:

code: This property is of type Number.

Object XPathEvaluator

The XPathEvaluator object has the following methods:

createExpression(expression, resolver): This method returns a XPathExpression object.
The expression parameter is of type String.
The resolver parameter is a XPathNSResolver object.
This method can raise a XPathException object or a DOMException object.
createResult(): This method returns a XPathResult object.
createNSResolver(nodeResolver): This method returns a XPathNSResolver object.
The nodeResolver parameter is a Node object.
evaluate(expression, contextNode, resolver, type, result): This method returns a XPathResult object.
The expression parameter is of type String.
The contextNode parameter is a Node object.
The resolver parameter is a XPathNSResolver object.
The type parameter is of type Number.
The result parameter is a XPathResult object.
This method can raise a XPathException object or a DOMException object.

Object XPathExpression

The XPathExpression object has the following methods:

evaluate(contextNode, type, result): This method returns a XPathResult object.
The contextNode parameter is a Node object.
The type parameter is of type Number.
The result parameter is a XPathResult object.
This method can raise a XPathException object or a DOMException object.

Object XPathNSResolver

The XPathNSResolver object has the following methods:

lookupNamespaceURI(prefix): This method returns a String.
The prefix parameter is of type String.

Prototype Object XPathResult

The XPathResult class has the following constants:

XPathResult.ANY_TYPE: This constant is of type Number and its value is 0.
XPathResult.NUMBER_TYPE: This constant is of type Number and its value is 1.
XPathResult.STRING_TYPE: This constant is of type Number and its value is 2.
XPathResult.BOOLEAN_TYPE: This constant is of type Number and its value is 3.
XPathResult.NODE_SET_TYPE: This constant is of type Number and its value is 4.
XPathResult.SINGLE_NODE_TYPE: This constant is of type Number and its value is 5.

Object XPathResult

The XPathResult object has the following properties:

resultType: This read-only property is of type Number.
numberValue: This read-only property is a double object and can raise a XPathException object on retrieval.
stringValue: This read-only property is of type String and can raise a XPathException object on retrieval.
booleanValue: This read-only property is of type Boolean and can raise a XPathException object on retrieval.
singleNodeValue: This read-only property is a Node object and can raise a XPathException object on retrieval.

The XPathResult object has the following methods:

getSetIterator(ordered): This method returns a XPathSetIterator object.
The ordered parameter is of type Boolean.
This method can raise a XPathException object or a DOMException object.
getSetSnapshot(ordered): This method returns a XPathSetSnapshot object.
The ordered parameter is of type Boolean.
This method can raise a XPathException object or a DOMException object.

Object XPathSetIterator

The XPathSetIterator object has the following methods:

nextNode(): This method returns a Node object.
This method can raise a DOMException object.

Object XPathSetSnapshot

The XPathSetSnapshot object has the following properties:

length: This read-only property is of type Number.

The XPathSetSnapshot object has the following methods:

item(index): This method returns a Node object.
The index parameter is of type Number.
Note: This object can also be dereferenced using square bracket notation (e.g. obj[1]). Dereferencing with an integer index is equivalent to invoking the item method with that index.

Prototype Object XPathNamespace

The XPathNamespace class has the following constants:

XPathNamespace.XPATH_NAMESPACE_NODE: This constant is of type Number and its value is 13.

Object XPathNamespace

XPathNamespace has the all the properties and methods of the Node object as well as the properties and methods defined below.

The XPathNamespace object has the following properties:

ownerElement: This read-only property is a Element object.

Appendix D: Acknowledgements

Many people contributed to the DOM specifications (Level 1, 2 or 3), including members of the DOM Working Group and the DOM Interest Group. We especially thank the following:

Andrew Watson (Object Management Group), Andy Heninger (IBM), Angel Diaz (IBM), Arnaud Le Hors (W3C and IBM), Ashok Malhotra (IBM and Microsoft), Ben Chang (Oracle), Bill Smith (Sun), Bill Shea (Merrill Lynch), Bob Sutor (IBM), Chris Lovett (Microsoft), Chris Wilson (Microsoft), David Brownell (Sun), David Ezell (Hewlett Packard Company), David Singer (IBM), Dimitris Dimitriadis (Improve AB), Don Park (invited), Elena Litani (IBM), Eric Vasilik (Microsoft), Gavin Nicol (INSO), Ian Jacobs (W3C), James Clark (invited), James Davidson (Sun), Jared Sorensen (Novell), Jeroen van Rotterdam (X-Hive Corporation), Joe Kesselman (IBM), Joe Lapp (webMethods), Joe Marini (Macromedia), Johnny Stenback (Netscape/AOL), Jon Ferraiolo (Adobe), Jonathan Marsh (Microsoft), Jonathan Robie (Texcel Research and Software AG), Kim Adamson-Sharpe (SoftQuad Software Inc.), Lauren Wood (SoftQuad Software Inc., former chair), Laurence Cable (Sun), Mark Davis (IBM), Mark Scardina (Oracle), Martin Dürst (W3C), Mary Brady (NIST), Mick Goulish (Software AG), Mike Champion (Arbortext and Software AG), Miles Sabin (Cromwell Media), Patti Lutsky (Arbortext), Paul Grosso (Arbortext), Peter Sharpe (SoftQuad Software Inc.), Phil Karlton (Netscape), Philippe Le Hégaret (W3C, W3C team contact and Chair), Ramesh Lekshmynarayanan (Merrill Lynch), Ray Whitmer (iMall, Excite@Home, and Netscape/AOL), Rezaur Rahman (Intel), Rich Rollman (Microsoft), Rick Gessner (Netscape), Rick Jelliffe (invited), Rob Relyea (Microsoft), Scott Isaacs (Microsoft), Sharon Adler (INSO), Steve Byrne (JavaSoft), Tim Bray (invited), Tim Yu (Oracle), Tom Pixley (Netscape/AOL), Vidur Apparao (Netscape), Vinod Anupam (Lucent).

Thanks to all those who have helped to improve this specification by sending suggestions and corrections (Please, keep bugging us with your issues!).

D.1: Production Systems

This specification was written in XML. The HTML, OMG IDL, Java and ECMAScript bindings were all produced automatically.

Thanks to Joe English, author of cost, which was used as the basis for producing DOM Level 1. Thanks also to Gavin Nicol, who wrote the scripts which run on top of cost. Arnaud Le Hors and Philippe Le Hégaret maintained the scripts.

After DOM Level 1, we used Xerces as the basis DOM implementation and wish to thank the authors. Philippe Le Hégaret and Arnaud Le Hors wrote the Java programs which are the DOM application.

Thanks also to Jan Kärrman, author of html2ps, which we use in creating the PostScript version of the specification.

Glossary

Editors:: Arnaud Le Hors, W3C; Robert S. Sutor, IBM Research (for DOM Level 1)

Several of the following term definitions have been borrowed or modified from similar definitions in other W3C or standards documents. See the links within the definitions for more information.

API: An API is an Application Programming Interface, a set of functions or methods used to access some functionality.
document element: There is only one document element in a Document. This element node is a child of the Document node. See Well-Formed XML Documents in XML [XML].
document order: There is an ordering, document order, defined on all the nodes in the document corresponding to the order in which the first character of the XML representation of each node occurs in the XML representation of the document after expansion of general entities. Thus, the document element node will be the first node. Element nodes occur before their children. Thus, document order orders element nodes in order of the occurrence of their start-tag in the XML (after expansion of entities). The attribute nodes of an element occur after the element and before its children. The relative order of attribute nodes is implementation-dependent.
element: Each document contains one or more elements, the boundaries of which are either delimited by start-tags and end-tags, or, for empty elements by an empty-element tag. Each element has a type, identified by name, and may have a set of attributes. Each attribute has a name and a value. See Logical Structures in XML [XML].
logically-adjacent text nodes: Logically-adjacent text nodes are Text or CDataSection nodes that may be visited sequentially in document order without entering, exiting, or passing over Element, Comment, or ProcessingInstruction nodes.
live: An object is live if any change to the underlying document structure is reflected in the object.
model: A model is the actual data representation for the information at hand. Examples are the structural model and the style model representing the parse structure and the style information associated with a document. The model might be a tree, or a directed graph, or something else.
namespace prefix: A namespace prefix is a string that associates an element or attribute name with a namespace URI in XML. See namespace prefix in Namespaces in XML [XML Namespaces].
namespace URI: A namespace URI is a URI that identifies an XML namespace. This is called the namespace name in Namespaces in XML [XML Namespaces].
read only node: A read only node is a node that is immutable. This means its list of children, its content, and its attributes, when it is an element, cannot be changed in any way. However, a read only node can possibly be moved, when it is not itself contained in a read only node.
tokenized: The description given to various information items (for example, attribute values of various types, but not including the StringType CDATA) after having been processed by the XML processor. The process includes stripping leading and trailing white space, and replacing multiple space characters by one. See the definition of tokenized type.
well-formed document: A document is well-formed if it is tag valid and entities are limited to single elements (i.e., single sub-trees).

References

For the latest version of any W3C specification please consult the list of W3C Technical Reports available at http://www.w3.org/TR.

F.1: Normative references

DOM Level 3 Core: W3C (World Wide Web Consortium) Document Object Model Level 3 Core Specification, September 2001. Available at http://www.w3.org/TR/DOM-Level-3-Core
ECMAScript: ISO (International Organization for Standardization). ISO/IEC 16262:1998. ECMAScript Language Specification. Available from ECMA (European Computer Manufacturers Association) at http://www.ecma.ch/ecma1/STAND/ECMA-262.HTM
Java: Sun Microsystems Inc. The Java Language Specification, James Gosling, Bill Joy, and Guy Steele, September 1996. Available at http://java.sun.com/docs/books/jls
OMGIDL: OMG (Object Management Group) IDL (Interface Definition Language) defined in The Common Object Request Broker: Architecture and Specification, version 2.3.1, October 1999. Available from http://www.omg.org
XML Information set: W3C (World Wide Web Consortium) XML Information Set, October 2001. Available at http://www.w3.org/TR/2001/REC-xml-infoset-20011024
XPath 1.0: W3C (World Wide Web Consortium) XML Path Language (XPath) Version 1.0, November 1999. Available at http://www.w3.org/TR/1999/REC-xpath-19991116

F.2: Informative references

XML: W3C (World Wide Web Consortium) Extensible Markup Language (XML) 1.0, October 2000. Available at http://www.w3.org/TR/2000/REC-xml-20001006
XML Namespaces: W3C (World Wide Web Consortium) Namespaces in XML, January 1999. Available at http://www.w3.org/TR/1999/REC-xml-names-19990114

Document Object Model (DOM) Level 3 XPath Specification

Version 1.0

W3C Working Draft 31 October 2001

Abstract

Status of this document

Table of contents

Expanded Table of Contents

Copyright Notice

W3C Document Copyright Notice and License

W3C Software Copyright Notice and License

1. Document Object Model XPath

Table of contents

1.1. Introduction

1.2. Mapping DOM to XPath

1.2.1. Text Nodes

1.2.2. Namespace Nodes

1.2.3. Document order

1.3. Interfaces

Appendix A: IDL Definitions

xpath.idl:

Appendix B: Java Language Binding

B.1: Other XPath interfaces

org/w3c/dom/xpath/XPathException.java:

org/w3c/dom/xpath/XPathEvaluator.java:

org/w3c/dom/xpath/XPathExpression.java:

org/w3c/dom/xpath/XPathNSResolver.java:

org/w3c/dom/xpath/XPathResult.java:

org/w3c/dom/xpath/XPathSetIterator.java:

org/w3c/dom/xpath/XPathSetSnapshot.java:

org/w3c/dom/xpath/XPathNamespace.java:

Appendix C: ECMAScript Language Binding

Appendix D: Acknowledgements

D.1: Production Systems

Glossary

References

F.1: Normative references

F.2: Informative references

Index

ANY_TYPE	API 1, 2

BOOLEAN_TYPE	booleanValue

createExpression	createNSResolver	createResult

document element	document order 1, 2	DOM Level 3 Core 1, 2, 3, 4

ECMAScript	element 1, 2, 3	evaluate 1, 2

getSetIterator	getSetSnapshot

INVALID_EXPRESSION_ERR	item

Java

length	live 1, 2	logically-adjacent text nodes 1, 2
lookupNamespaceURI

model 1, 2

namespace prefix 1, 2, 3, 4	namespace URI 1, 2, 3, 4	nextNode
NODE_SET_TYPE	NUMBER_TYPE	numberValue

OMGIDL	ownerElement

read only node 1, 2	resultType

SINGLE_NODE_TYPE	singleNodeValue	STRING_TYPE
stringValue

tokenized	TYPE_ERR

well-formed document

XML 1, 2, 3	XML Information set 1, 2	XML Namespaces 1, 2, 3
XPath 1.0 1, 2, 3	XPATH_NAMESPACE_NODE	XPathEvaluator
XPathException	XPathExpression	XPathNamespace
XPathNSResolver	XPathResult	XPathSetIterator
XPathSetSnapshot