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XPath (XML Path Language) is an expression language designed to support the query or transformation of XML documents. It was defined by the World Wide Web Consortium (W3C) in 1999, [1] and can be used to compute values (e.g., strings, numbers, or Boolean values) from the content of an XML document.
The "/" operator is generalized in XPath 2.0 to allow any kind of expression to be used as an operand: in XPath 1.0, the right-hand side was always an axis step. For example, a function call can be used on the right-hand side. The typing rules for the operator require that the result of the first operand is a sequence of nodes.
XPointer is a system for addressing components of XML-based Internet media. It is divided among four specifications: a "framework" that forms the basis for identifying XML fragments, a positional element addressing scheme, a scheme for namespaces, and a scheme for XPath-based addressing.
For instance, the XML document and the ASCII tree have the same structure. XML Trees do not show the content in an Instance document, only the structure of the document. In this example Product is the Root Element of the tree and the two child nodes of Product are Name and Details. Details contains two child nodes, Description and Price.
Compared to XPath 2.0, XPath 3.0 adds the following new features: . Inline function expressions Anonymous functions can be created in an expression context. For example, the expression function ($ a as xs:double, $ b as xs:double) as xs:double {$ a * $ b} creates a function that returns the product of its two arguments.
The XQuery and XPath Data Model (XDM) is the data model shared by the XPath 2.0, XSLT 2.0, XQuery, and XForms programming languages. It is defined in a W3C recommendation . [ 1 ] Originally, it was based on the XPath 1.0 data model which in turn is based on the XML Information Set .
It was difficult to see how to give XPath 2.0 proper coverage within that article, given that there are so many differences in the fundamental concepts of the two versions; the simplest approach seemed to be to create a new XPath 2.0 article, rename the existing article as XPath 1.0, and create a new XPath article to point to the two.
XQuery includes XPath as a sub-language and XML itself is a valid sub-syntax of XQuery. In addition to XPath, some XML databases support XSLT as a method of transforming documents or query results retrieved from the database.