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Back to the future with XML
A truly excellent bit of overview and opinion, Kendall Grant Clark's recent squib for XML.com is entitled "XHTML is the Most Important XML Vocabulary". Here, Clark reminds us that although XML is amenable (and put) to all kinds of interesting uses from anatomy to zoology, the real power of the Web remains rooted in HTML. Therefore, XHTML has a better chance to raise "XML consciousness" in the general public than many other forms of XML that might not attract as much attention or interest from run-of-the-mill content creators and casual users.
He uses this assertion to review for us what's up with XHTML (working drafts of an XHTML 2.0 specification are currently underway, and subjects of frequent and often active debate) and to remind us that like it or not, this relatively pedestrian use for XML is important to many professionals who may never fully master XML itself. He also speaks in several interesting ways about the trade-offs between purity and convenience, especially when it comes to separating content from presentation (always a touchy subject for markup mavens).
From the latest draft of XHTML 2.0 dated May 6, 2003, Clark calls attention to numerous interesting markup and infrastructure elements:
- Although the RELAX NG schema language is not a W3C specification, it is often recognized as the easiest and most document-friendly of the various XML-based metalanguages (XML was originally defined using SGML, but may also be defined using XML-based vocabularies as well; purists find the latter more appealing since it requires learning only one set of grammar, syntax, and document structure). The W3C is starting to find a place for this notation in its acceptable canons of metadata.
- XHTML includes an edit attribute for numerous elements, which permits document elements to carry information that explains "how, when and why content has changed." If XHTML is to be used for documents that go through formal editorial processes, such information can be very important.
- The style attribute is back: Early drafts of the XHTML 2.0 specification eliminated the style attribute that allows use of Cascading Style Sheet (CSS) markup to control presentation of XHTML content. A bone of contention in the XHTML community, style is, IMHO, useful, familiar and appreciated by many content developers and document designers. If purists don't want to use it, they can ignore it (but if it's out altogether, nobody can use it, so I hope the working group keeps it in for the final recommended version of the spec).
- XHTML 2.0 adds a new <blockcode> ... </blockcode> element to permit inclusion of executable code right inside XHTML documents. For programmers who build lots of code widgets, or content developers smart enough to find and use such things, this can add great things to Web documents (and pages).
- XHTML 2.0 also adds a <caption> ... </caption> element that may appear within table or object elements, for easier labeling of such constructs within documents.
In general, Clark's opinion is that XHTML 2.0 is headed in the right direction and that ordinary content developers will be inclined to appreciate not just its capabilities but also its relative simplicity and ease of use. For what it's worth, I agree wholeheartedly myself.
About the Author
Ed Tittel is a 20-plus year veteran of the computing industry, who's worked as a programmer, manager, systems engineer, instructor, writer, trainer, and consultant. He's also the series editor of Que Certification's Exam Cram 2 and Training Guide series, and writes and teaches regularly on Web markup languages and related topics.
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