Before learning XPath, we should first understand XSL which stands for Extensible Stylesheet Language. It is similar to XML as CSS is to HTML.
Need for XSL
In case of HTML documents, tags are predefined such as table, div, span, etc. The browser knows how to add style to them and display them using CSS styles. But in case of XML documents, tags are not predefined. In order to understand and style an XML document, World Wide Web Consortium (W3C) developed XSL which can act as an XML-based Stylesheet Language. An XSL document specifies how a browser should render an XML document.
Following are the main parts of XSL −
- XSLT − used to transform XML documents into various other types of document.
- XPath − used to navigate XML documents.
- XSL-FO − used to format XML documents.
What is XPath?
XPath is an official recommendation of the World Wide Web Consortium (W3C). It defines a language to find information in an XML file. It is used to traverse elements and attributes of an XML document. XPath provides various types of expressions which can be used to enquire relevant information from the XML document.
- Structure Definitions − XPath defines the parts of an XML document like element, attribute, text, namespace, processing-instruction, comment, and document nodes
- Path Expressions − XPath provides powerful path expressions select nodes or list of nodes in XML documents.
- Standard Functions − XPath provides a rich library of standard functions for manipulation of string values, numeric values, date and time comparison, node and QName manipulation, sequence manipulation, Boolean values etc.
- Major part of XSLT − XPath is one of the major elements in XSLT standard and is must have knowledge in order to work with XSLT documents.
- W3C recommendation − XPath is an official recommendation of World Wide Web Consortium (W3C).
One should keep the following points in mind, while working with XPath −
- XPath is core component of XSLT standard.
- XSLT cannot work without XPath.
- XPath is basis of XQuery and XPointer.