It is often desirable to be able to transform one vocabulary of elements and attributes into another. There are different ways of communicating information that require the use of other vocabularies. Special purpose vocabularies also need to be tansfomed for use with browsers or rendering engines.

Presentation has long ben a concern of the stuctured information community. With SGML a standardized language (DSSSL) was developed to support the tansformation of instances of a certain document type into those of another document type, and provide suitable output for rendering software.

The Extensible Stylesheet Language Transformations (XSLT) language is the W3C stylesheet vocabulary for transforming XML instances into instances of the same or another vocabulary. Stylesheets (which are themselves instances of XML documents) are written to drive an XSLT processor to produce our desired results from our information. The XML Path Language (XPath) is the W3C syntax for addressing components of an XML instance. XPath plays a major role in the stylesheets we write using XSLT. XSLT and XPath give us the power to transform structured information into a myriad of results: from simple text, to Hypertext Markup Language (HTML), to any arbitrary XML vocabulary.

It is often necessary to convert XML into a format suitable for printing. When producing a paginated presentation of XML information, a different set of navigation tools to those available online are needed. These navigational aids include headers, footers, page numbers and page number citations.

Many aspects of pint layout are applicable on electronic displays and Recommendations such as Cascading Stylesheets (CSS) have defined presentation parameters in areas such as font, margin, and color properties. Paginating marked-up information is not something new, in that the Document Style Semantics and Specification Language (DSSSL) is an international standard for use originally with SGML documents, though it also works unchanged with XML documents.

The W3C has defined a collection of pagination parameters for print-oriented rendering. These pagination semantics are equally suitable for an electronic display of fixed-size folios of information, such as page-turner browsers and Portable Document Format (PDF) readers.The Extensible Stylesheet Language (XSL), also known colloquially in our community as the Extensible Stylesheet Language Formatting Objects (XSLFO), combines the heritage of CSS and DSSSL in a well-thought-out and robust specification of formatting semantics for paginating information.