XSL

What is XSL?

XSL stands for Extensible Stylesheet Language

CSS was designed for styling HTML pages, and can be used to style XML pages

XSL was designed specifically to style XML pages, and is much more sophisticated than CSS

XSL consists of three languages:

XSLT (XSL Transformations) is a language used to transform XML documents into other kinds of documents (most commonly HTML, so they can be displayed)

XPath is a language to select parts of an XML document to transform with XSLT

XSL-FO (XSL Formatting Objects) is a replacement for CSS

How does it work?

The XML source document is parsed into an XML source tree

You use XPath to define templates that match parts of the source tree

You use XSLT to transform the matched part and put the transformed information into the result tree

The result tree is output as a result document

Parts of the source document that are not matched by a template are typically copied unchanged

Simple XPath

XPath expressions look a lot like paths in a computer file system

/ means the document itself (but no specific elements)

/library selects the root element

/library/book selects every book element

//author selects every author element, wherever it occurs

Simple XSLT

loops through every book element, everywhere in the document

chooses the content of the title element at the current location

    chooses the content of the title element for each book in the XML document

What we need to do

We need to save our XML into a file (let’s call it books.xml)

We need to create a file (say, books.xsl) that describes how to select elements from books.xml and embed them into an HTML page

We do this by intermixing the HTML and the XSL in the books.xsl file

We need to add a line to our books.xml file to tell it to refer to books.xsl for formatting information

How to use it

In a modern browser, such as Netscape 6, Internet Explorer 6, or Mozilla 1.0, you can just open the XML file

Older browsers will ignore the XSL and just show you the XML contents as continuous text

You can use a program such as Xalan, MSXML, or Saxon to create the HTML as a file

This can be done on the server side, so that all the client side browser sees is plain HTML

The server can create the HTML dynamically from the information currently in XML