XPath expressions

The XML Path Language (XPath) is an XSL sub-language designed to uniquely identify or address parts of a source XML document. An XPath expression can be used to search through an XML document, and extract information from the nodes (any part of the document, such as an element or attribute) in it.

There are four different kinds of XPath expressions:

Boolean
An expression type with two possible values. 
Node set 
A collection of nodes that match an expression's criteria, usually derived with a location path. 
Number
A numeric value, useful for counting nodes and for performing simple arithmetic.
String 
A fragment of text that can be from the input tree, processed or augmented with general text.

An XPath expression returns a certain node set, which is a collection of nodes. For example, if you tell XPath to look for any element with an id attribute, there can be more than one. XPath returns a node set, which is a collection of all the elements in the input document that have an id element.

This is a sample XPath expression:

/order/item/part-number

Which means "select any elements named part-number, which are children of item elements, which are children of order elements which are children of the document root.

You can create an XPath expression using the XPath Expression wizard. You can launch the XPath Expression wizard in the following ways:

Related tasks
Creating XPath expressions
Related information
XPath on w3

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