Overview

Document transformation is an important issue for XML. Because XML allows the storage of information in a presentation-neutral format, it becomes necessary to transform this content into a presentation format such as HTML, WML, or PDF when clients ask for that information.

In this chapter we will give a short overview of XSLT, an XML-based transformation language. We introduce two opposing programming styles and discuss the virtues and deficiencies of XSLT. Because XSLT draws heavily on XPath, please refer to the discussion of XPath in Section 2.5.1.

XSLT has a reputation of not scaling very well. Although this doesn t matter for the purposes of prototyping and ad hoc solutions, it is an issue when it comes to enterprise computing. We will discuss performance problems and look for alternatives.

Historically XSLT was a part of the XSL (Extensible Stylesheet Language) specification, but then XSL was split into three parts: XPath, XSLT, and Formatting Objects (XFO). XSLT is now a recommendation in its own right (Clark 1999a). The purpose of XSLT is to enable style-sheet-controlled transformations from one XML document format into another document format (XML or non-XML, but mostly HTML).

Applications of XSLT

When you think about it, XSLT can unleash substantial power:

• XSLT can be used to transform presentation-neutral XML data into presentational formats such as XHTML, XForms, WML, SMIL, SVG, and so on.

• It can be used to convert document instances when a new version of a schema is introduced. It can be used to harvest RDF statements...