XPath
{{About||XPath 1.0|XPath 1.0}}
XPath (XML Path Language) is a language for selecting nodes from an
XML document. In addition, XPath may be used to compute values (strings, numbers, or boolean values) from the content of an XML document. XPath was defined by the
World Wide Web Consortium, W3C.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. 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 and
XForms. There are currently two versions in use.
XPath 1.0 became a Recommendation on 16 November 1999 and is widely implemented and used, either on its own (called via an API from languages such as
Java or
C#), or embedded in languages such as
XSLT or
XForms.The current version of the language is
XPath 2.0, which became a Recommendation on 23 January 2007. A number of implementations exist but they are not yet as widely used as XPath 1.0. XPath 2.0 is a very much larger language than XPath 1.0, and changes some of the fundamental concepts of the language such as its type system, and hence is described in a separate article.The most notable change is that XPath 2.0 has a much richer type system; XPath 2.0 supports atomic types, defined as built-in types in
XML Schema, and may also import user-defined types from a schema. 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. It offers a
for expression which is 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.
External links
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