Learning XML

1.8. Transformation

It may sound like something out of science fiction, but transforming documents is an important part of XML. An XML transformation is a process that rearranges parts of a document into a new form. The result is still XML, but it may be radically different from the original. Think of it as a food processor for information.

One purpose of transforming a document is to convert from one XML application to another. For example, suppose you have written a document in an XML application you invented. The document cannot be viewed in older browsers that understand only HTML, but you can transform it into XHTML through a transformation. This retains all the content while changing the markup, and allows your document to be viewed even by HTML-only browsers.

Transformation can also be used to filter a document, retaining only a portion of the original. You can generate excerpts or summaries of a document, for example to total up your expenditures in a checkbook or print the section titles of a book to generate a table of contents.

Documents are transformed by using the Extensible Style Language for Transformations (XSLT). You write XSLT transformation instructions in a document resembling a stylesheet, and then use a transformation engine to generate a result.

1.8.1. Transformation Engines

The following are a few useful transformation engines that can be used with XSLT to transform XML documents:

XT

This fast and simple transformation engine was written in Java by ...