| Paradigm(s) | Query language |
|---|---|
| Appeared in | 1999 |
| Developer | W3C |
| Stable release | 2.0 (2007-01-23) |
| Major implementations | C#, Java, JavaScript |
| Influenced by | XSLT, XPointer |
| Influenced | XML Schema, XForms |
XPath, the 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 was defined by the World Wide Web Consortium (W3C).
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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.[1] In popular use (though not in the official specification), an XPath expression is often referred to simply as an XPath.
Originally motivated by a desire to provide a common syntax and behavior model between XPointer and XSLT, subsets of the XPath query language are used in other W3C specifications such as XML Schema, XForms and the Internationalization Tag Set (ITS).
XPath has been adopted to a number of XML processing libraries and tools, many of which also offer CSS Selectors, another W3C standard, as a simpler alternative to XPath.
Two versions of XPath are currently in use.
The most notable change is that XPath 2.0 has a much richer type system.[2] Every value is now a sequence (a single atomic value or node is regarded as a sequence of length one). XPath 1.0 node-sets are replaced by node sequences, which may be in any order.
To support richer type sets, XPath 2.0 offers a greatly expanded set of functions and operators.
XPath 2.0 is in fact a subset of XQuery 1.0. They share the same query data model (XDM). It offers a for expression which is a cut-down version of the "FLWOR" expressions in XQuery. It is possible to describe the language by listing the parts of XQuery that it leaves out: the main examples are the query prolog, element and attribute constructors, the remainder of the "FLWOR" syntax, and the typeswitch expression.
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