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4. XPath reference

The XPath language is used to describe locations in a document tree. It is the expression language used by XSLT. See the XPath specification for complete details.

A well-formed XML document can be visualized as a tree (in the computer science meaning of the term), and this view is used throughout XPath and XSLT. For example, if a certain document represents a book, it might have a top-level tag <book>, containing elements like <chapter> and <appendix>.

A few important definitions:

4.1. Data types in XPath

XPath expressions use these data types:


Many XPath operations select a set of zero or more nodes. For example, the expression "address" selects all of the <address> elements that are children of the context node. This node-set may contain no nodes, one node, or many.


A true or false value.


Numbers in XPath are represented using floating point.


A string of characters.