XSLT is a language for transforming XML documents.
XPath is a language for navigating in XML documents.
XQuery is a language for querying XML documents.
XSL stands for EXtensible Stylesheet Language.
The World Wide Web Consortium (W3C) started to develop XSL because there was a need for an XML-based Stylesheet Language.
HTML uses predefined tags. The meaning of, and how to display each tag is well understood.
CSS is used to add styles to HTML elements.
XML does not use predefined tags, and therefore the meaning of each tag is not well understood.
A <table> element could indicate an HTML table, a piece of furniture, or something else - and browsers do not know how to display it!
So, XSL describes how the XML elements should be displayed.
XSL consists of four parts:
With the CSS3 Paged Media Module, W3C has delivered a new standard for document formatting. So, since 2013, CSS3 is proposed as an XSL-FO replacement.
XSLT is the most important part of XSL.
XSLT is used to transform an XML document into another XML document, or another type of document that is recognized by a browser, like HTML and XHTML. Normally XSLT does this by transforming each XML element into an (X)HTML element.
With XSLT you can add/remove elements and attributes to or from the output file. You can also rearrange and sort elements, perform tests and make decisions about which elements to hide and display, and a lot more.
A common way to describe the transformation process is to say that XSLT transforms an XML source-tree into an XML result-tree.
XSLT uses XPath to find information in an XML document. XPath is used to navigate through elements and attributes in XML documents.
If you want to study XPath first, please read our XPath Tutorial.
In the transformation process, XSLT uses XPath to define parts of the source document that should match one or more predefined templates. When a match is found, XSLT will transform the matching part of the source document into the result document.
All major browsers support XSLT and XPath.
XSLT became a W3C Recommendation 16. November 1999.