Make the most of XSL-FO; lively up those Web services!

[PROGRAMMERS REPORT, OCTOBER 22, 2002] -- XML has been asked to do a lot since its startling inception in the late '90s. The same is true for a host of XML-related standards. Although conceptually simple, implementation of these standards, especially when coupled with complex Java and .NET environments, can be challenging in the hands of newcomers. And few in XML are not in the category of newcomer.

One highly versed ''XML-ist'' is G. Ken Holman of Crane Softwrights Ltd. He has served many years in high-tech, taking part in efforts to create videotext systems (those forgotten predecessors to the Web) and SGML document systems. He is the author of Definitive XSLT and XPath (Prentice Hall PTR, 2001), and former chair of the OASIS XML Conformance Technical Subcommittee. These days, Holman's efforts center on training people in the use of XSLT, which allows systems to transform documents conforming to the Extensible Stylesheet Language standard for expressing stylesheets.

Among matters that concern Holman, as he watches XML spread and evolve, is the treatment of documents. In XML-based Web services especially, he noted in a recent conversation with Programmers Report, the rush to create machine-to-machine communications systems often ignores the still-important role printed documents play in business-to-business (B2B) efforts.

B2B efforts aside, the notion of Web services for consumers implies that many people, including many grandmas and grandpas used to holding documents, must be comfortable with the process. Holman wonders if Web services creators are aware of a companion recommendation to XSLT known as XSL-FO (for Extensible Stylesheet Language Formatting Objects), which provides a framework for the useful formatting of semantics for paginating information for better browser navigation and print support.

''No one accepts print from a Web browser as a quality paginated result. No one likes printing their browser screen,'' said Holman. ''The ubiquitous final form for print from the Web today is PDF.'' A solution here is XSL-FO, which Holman describes as ''an XML vocabulary for paginating structured information.

''I think Web service implementers are ignoring whole constituencies of print users who refuse to read the screen and who want to use paper,'' added Holman.

He noted that using XSL-FO allows developers to produce results to make the ''paper Web experience decidedly better.''

Whither XSLT?
A lot of people are learning XSLT these days. What they think about it may vary according to what they do with it. One misunderstanding may be that it is ‘a language,’ as in ‘a programming language.’

“Some people claim XSLT is a bad programming language, and I agree,” said Holman. “It should not be regarded as a programming language. It should be described as a templating language.” Understood as such, it may be made more accessible to nonprogrammers, Holman indicated.

To work effectively with XSLT, users should realize that it was designed more for template implementers, than for template writers, Holman indicated. “The goal of XSLT is to supply the [XSLT] processor with enough examples so it can assemble the result from them,” he said.

When people try to use XSLT as a programming language, missteps may follow.

What is XSL-FO? Ken Holman on
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About the Author

Jack Vaughan is former Editor-at-Large at Application Development Trends magazine.


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