XPath Syntax

The XPath expression uses a path notation like URLs, for addressing parts of an XML document. The expression is evaluated to yield an object of the node-set, Boolean, number, or string type. For example, the expression book/author will return a node-set of the <author> elements contained in the <book> elements, if such elements are declared in the source XML document.

In XPath, path expression is used to select nodes or node-sets in an XML document. The node is selected by following a path or steps.

Let's take an example to see the syntax of XPath. Here, we take an XML document.

<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
<book>
  <title lang="en">Three Mistakes of My Life</title>
  <price>110</price>
</book>
<book>
  <title lang="en">Immortals of Meluha</title>
  <price>200</price>
</book>
</bookstore>

Selecting Nodes

Path expressions used for selecting nodes are:

Index	Expression	Description
1)	nodename	Selects all nodes with the name "nodename"
2)	/	Selects from the root node.
3)	//	Selects nodes in the document from the current node that match the selection no matter where they are.
4)	.	Selects the current node
5)	..	Selects the parent of the current node
6)	@	Selects attributes

See the path expressions and their details in the above example:

Path Expression	Result
bookstore	Selects all nodes with the name "bookstore"
/bookstore	Selects the root element bookstore. Note: if the path starts with a slash ( / ) it always represents an absolute path to an element!
bookstore/book	Selects all book elements that are children of bookstore.
//book	Selects all book elements no matter where they are in the document.
bookstore//book	Selects all book elements that are descendant of the bookstore element, no matter where they are under the bookstore element.
//@lang	Selects all attributes that are named lang.

Predicates

Predicates are used to find a specific node or a node that contains a specific value.

Predicates are always embedded in square brackets.

In the table below we have listed some path expressions with predicates and the result of the expressions:

Path Expression	Result
/bookstore/book[1]	Selects the first book element that is the child of the bookstore element. Note: In IE 5,6,7,8,9 first node is[0], but according to W3C, it is [1]. To solve this problem in IE, set the selectionlanguage to XPath: in JavaScript: xml.setProperty("SelectionLanguage","XPath");
/bookstore/book[last()]	Selects the last book element that is the child of the bookstore element.
/bookstore/book[last()-1]	Selects the last but one book element that is the child of the bookstore element.
/bookstore/book[position()<3]	Selects the first two book elements that are children of the bookstore element.
//title[@lang]	Selects all the title elements that have an attribute named lang.
//title[@lang='en']	Selects all the title elements that have a "lang" attribute with a value of "en".
/bookstore/book[price>100]	Selects all the book elements of the bookstore element that have a price element with a value greater than 100
/bookstore/book[price>100]/title	Selects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 100

Selecting Unknown Nodes

XPath wildcards are used to select unknown XML nodes.

Wildcard	Description
*	Matches any element node
@*	Matches any attribute node
node()	Matches any node of any kind

See this in above example:

Path Expression	Result
/bookstore/*	Selects all the child element nodes of the bookstore element
//*	Selects all elements in the document
//title[@*]	Selects all title elements which have at least one attribute of any kind

Selecting Several Paths

The | operator is used in XPath expression to select several paths. From the above example, we have listed some path expressions and result of the expressions.

Path Expression	Result
//book/title \| //book/price	Selects all the title and price elements of all book elements
//title \| //price	Selects all the title and price elements in the document
/bookstore/book/title \| //price	Selects all the title elements of the book element of the bookstore element and all the price elements in the document

Next TopicXPath Absolute Path

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