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What's up with XML 2.0?

Ed Tittel discusses the new version of XML 2.0 and the characteristics that differentiate it from the original XML.

No sooner does one standard make it through whatever official processes its parent organization requires for approval, than another version, add-on or successor seems to rear its head. I tend to look at this as a sort of adult version of "the bear went over the mountain" intended as much to keep standards and technology-makers out of idle mischief as much as it represents the inexorable march of progress and technology toward ever newer, better and often more complex implementations of the same old thing.

All this tongue in cheek musing on the banes and benefits of progress comes as a result of turning toward the successor specification to XML 1.0 and 1.1—namely XML 2.0. The original impetus of XML that pervades both 1.0 and 1.1 versions was to make order out of chaos, impose standard syntax and structure (thus these markup languages are deliberately very readable, both for humans and machines) and facilitate mechanisms to foster data interchange and exchange among all kinds of producers and consumers of information, services and content.

As far back as 2002, the Technical Architecture Group at the W3C started considering musings on the nature and future of XML 2.0. In fact, XML visionary and developer Tim Bray, who also played a key role in formulating XML 1.0, kicked off efforts to formulate an XML 2.0 successor by describing a "skunkworks" version with the following basic characteristics:

  • Keep the basic syntax and structure of XML 1.0
  • Lose the legacy metalanguage support from SGML (document type definitions, or DTDs, in more specific terms) and lean on an XML-based metalanguage (which ultimately led to XML Schema, RELAX NG and so forth)
  • Add the use of XML namespaces, plus the XML Base and XML Infoset specifications

What drove this early version of XML 2.0 is in large part identical to what drove its predecessors—primarily, further movement toward simplicity (all XML, all the time) and consistent use of markup elements, attributes and values.

But despite all the work on XML, and even more work using XML to create applications and markup languages that range from annotations to zoology, XML has not yet made a major impact directly on the World Wide Web. This is particularly true if one looks at the number of sites that publish content directly in XML format (as documents that typically end in an .xml file extension). Rather, most sites tend to house XML inside content management systems, databases and other document repositories with publishing engines, and to use XSLT or other techniques to transform XML into HTML for Web delivery.

Where is XML 2.0 in all of this? A quick look at the XML Core Working Group (the gang inside the W3C Architecture Domain responsible for the formal XML specification and its development and maintenance) public page makes no mention of XML 2.0, nor does the Extensible Markup Language (XML) activity page or activity statement. Even a search on XML 2.0 at the W3C turns up little or no mention outside the 2002 conference at which Tim Bray elaborated his thoughts on what an XML 2.0 might look like.

Does this mean that XML 2.0 is either moribund or dead? Not necessarily. In a fascinating article entitled "Is XML 2.0 Under Development" XML maven Micah Dubinko cites work involving no less a markup luminary than Tim Berners-Lee himself, that may seek to bridge the continuing divide between HTML and XML. He speculates that there may already be an effort underway to reinvent XML. He speculates further that it will probably seek to do for ordinary Web sites and pages what the various XHTML modularizations created specifically for use on mobile devices has done for that user community—namely to offer a simple, coherent and workable markup model that uses XML's capabilities to help users make the most of their online experiences. In other words, he believes that this effort will seek to extend these kinds of benefits to Web users outside the mobile device space. He has some reservations about what's going on, primarily because of a narrow focus on updating/rationalizing HTML may not leave as much room for unexpected uses and technology innovation as a more open-ended approach.

But the wild, wacky and sometimes even woolly World Wide Web specification process still leaves enough room for public comment and participation that however narrow current efforts may be, working through the approval process will perforce provide ample opportunities to open things up and possibly even rationalize them for broader applications. Thus, while the future and even the contents and capabilities of XML 2.0 are still largely up for grabs, and still pretty mysterious, the mystery should start unfolding soon as various draft specifications are released and become the focus of public debate and discussion. I don't think we can expect an XML 2.0 recommendation any time soon, and probably not even in the next two to three years, but you can expect to start hearing lots of cussing and discussing on this and related topics in the very near future (certainly before 2007 draws to a close).

About the author

Ed Tittel is a full-time writer and trainer whose interests include XML and development topics, along with IT Certification and information security topics. Among his many XML projects are XML For Dummies, 4th edition, (Wylie, 2005) and the Shaum's Easy Outline of XML (McGraw-Hill, 2004). E-mail Ed at with comments, questions, or suggested topics or tools for review.

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