Picking Your Style of XSL

XML's style needs are pretty extensive. Clean XML document structures are rarely in the form you need for presentation, and you may need to present the same XML document in several ways — in

print, on the screen, or even in a multimedia presentation. In addition, for those who want to take full advantage of XML's power as a tool for sharing data across systems, there should be an easy way to convert documents from one vocabulary to another.

The architects of XML have you covered. They decided that the responsibility for display and for document conversion should be handled by a separate mechanism rather than XML proper, so they developed XSL as a special vocabulary of XML, designed to describe stylesheets for XML documents. During development, these same architects realized that creating one mechanism for both display and conversion was a Herculean task. So they split the style and conversion mechanisms of XSL into two different but related mechanisms:

• XSL Transformations (XSLT) handles the conversion from one set of markup to another.

• XSL Formatting Objects (XSL-FO) helps you format XML for devices that want to display XML.

XSLT

The first and most well-developed face of XSL is a conversion tool known as XSLT. The T stands for transformation, and that's exactly what this part of XSL is designed to do — use a set of rules to transform (that is, convert) documents described by one set of elements into documents described by another set of elements. The two sets of elements don't even have to look anything alike.