With Extensible Stylesheet Language Formatting Objects (XSL-FO), an XML application for presentation, any user agent can render content to the exact specifications given by the developer. Discover the relationships between XSL-FO, XHTML, Cascading Style Sheets (CSS), and Extensible Stylesheet Language Transformations (XSLT).
Extensible Stylesheet Language Formatting Objects (XSL-FO) [W3C Recommendation] is a presentation language defined in XML. (Note: The title of the linked specification is "Extensible Stylesheet Language (XSL)," but the content is actually just the formatting objects aspects of XSL.) XSL-FO is an XML format that can be used by any user agent to render content to the precise specifications given by the developer. Its role is similar to that of XHTML in Web user interfaces, but it is more complex and allows for the expression of formatting details suitable for print publication. These details are not unlike those specified in Cascading Style Sheets (CSS), but in XSL-FO, the details make up the substance of the markup language itself rather than instructions for rendering separate markup.
XSL-FO is sometimes used as an output format from Extensible Stylesheet Language Transformations (XSLT). In fact, originally XSLT and XSL-FO were to be a single system called XSL, but the working group wisely split the two parts into two separate specifications. The naming is a bit confusing, so just remember that almost everyone uses the short name "XSL-FO" for "Extensible Stylesheet Language (XSL)," and on the other hand, XSLT has nothing to do with style. A variety of open source and commercial tools can translate XSL-FO to TeX, Adobe's PDF, and other (non-XML) output formats suitable for print and typesetting. XSL-FO has become popular because of this usage pattern, but it has always aimed to work as a native rendering format for WYSIWYG tools and the like, and it is beginning to gain traction in such usage. XSL-FO 1.1 [W3C Recommendation] is an update to the language that adds features such as change annotations, indexes, bookmarks, and enhancements to the handling of graphics.
- Using XSL-FO to create printable documents by Rodolfo M. Raya focuses on the use of XSL-FO for printable database reports (developerWorks, November 2001).
- Using XSL Formatting Objects by J. David Eisenberg is a brief introduction that highlights the strong internationalization of XSL-FO (O'Reilly xml.com, January 2001).
- ZVON offers an XSL FO reference that maps out some relationships of elements but does not go into much depth on each element's semantics.
- Dave Pawson's XSL FAQ covers XSL-FO as well as XSLT and XPath.
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