XML XPath Syntax


This post is based on the XPath tutorial at w3schools.com. XPATH (XML Path Language) is a query language for selecting nodes from an XML document. In addition, XPath may be used to compute values (e.g., strings, numbers, or Boolean values) from the content of an XML document. XPath uses path expressions to select nodes or node-sets in an XML document. The node is selected by following a path or steps.

The XPath language is based on a tree representation of the XML document, and provides the ability to navigate around the tree, selecting nodes by a variety of criteria. In popular use (though not in the official specification), an XPath expression is often referred to simply as “an XPath”.

There are several versions of XPath in use. XPath 1.0 was published in 1999, XPath 2.0 in 2007, and XPath 3.0 in 2014. Version 3.1 is at Proposed Recommendation status (as of February 2017). However, XPath 1.0 is still the version that is most widely available.

<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
  <book>
    <title lang="en">Harry Potter</title>
    <price>29.99</price>
  </book>
  <book>
    <title lang="en">Learning XML</title>
    <price>39.95</price>
  </book>
</bookstore>

Selecting Nodes

XPath uses path expressions to select nodes in an XML document. The node is selected by following a path or steps. The most useful path expressions are listed below:

Expression Description
nodename Selects all nodes with the name “nodename
/ Selects from the root node
// Selects nodes in the document from the current node that match the selection no matter where they are
. Selects the current node
.. Selects the parent of the current node
@ Selects attributes

In the table below, w3schools.comĀ on their website, has listed some path expressions and the result of the expressions.

Path Expression Result
bookstore Selects all nodes with the name “bookstore”
/bookstore Selects the root element bookstoreNote: 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, from w3schools.com, 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>35.00] Selects all the book elements of the bookstore element that have a price element with a value greater than 35.00
/bookstore/book[price>35.00]/title Selects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 35.00

Selecting Unknown Nodes

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

In the table below we have listed some path expressions and the result of the expressions.

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

By using the | operator in an XPath expression you can select several paths. In the table below w3schools.com has listed some path expressions and the 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

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