Five challenges for XML
16:02, 18 Dec 2001 UTC | Eric van der Vlist

James Clark

James Clark, the first recipient of the IDEAlliance XML Cup Award and opening keynote speaker at XML 2001, gave a lively description of the five challenges facing the XML community.

1) Make progress without compromising the strength of XML

Clark described the main strength of XML as its diversity. XML "does everything from encoding SOAP procedure calls with a lifetime of a few milliseconds up to encoding Buddhist religious texts with a lifetime of millenniums," a power which emerges from its simplicity: "XML doesn't do much by itself… to me XML is a syntax for encoding a labeled tree". Clark urged XML's keepers to keep this original simplicity and generality by "separating out functionality that is general purpose, just dealing with this labeled tree from high levels that are specific to particular domains whether those domains are databases, or documents or web services or whatever." He presented as unfortunate counter-examples the cases of W3C XML Schema date types and the xsi:nil attribute.

2) Don't neglect the foundation

So many applications are now relying on XML that its foundation should be "rock solid" and Clark advised developers to "spend some time fixing the base" after giving a detailed list of things to fix such in XML 1.0. Highlights included "bizarre" behavior in XML 1.0, which "tells you that you need to report unparsed entities but not that you should report elements and attributes"; Namespaces in XML, XML Infoset and XML Base which should be included in the core standard; DTDs which are "basically one big mess" by mixing so many different features in a non XML syntax and for which we need "to learn to live without" and the character entities for which a replacement still needs to be found.

3) Fill in the missing pieces

The processing model is becoming complex and we currently process validation, inclusion, transformations and soon query processing. There is no generic solution for "controlling the processing pipeline". Each feature does processing its own way (doctype, xsi:schemaLocation, stylesheet location, etc.), and none of them is working terribly well.

4) Improve XML processing.

Noting that the current solutions to XML processing are just "too much work, too difficult, too error prone", Clark made a difference between using general-purpose languages with a XML API and using a XML specific language.

If you use generic programming languages to process XML, you need "a standard pull API" with readers and writers like those in .NET - just because it comes out of Microsoft is not necessary bad," and loosely coupled data binding interfaces "automating the process of mapping between the XML and the data model" even when the internal structure is not a tree but directed graphs.

If you use a XML-specific language, XSLT is the current choice even though "used for truly scary things". XSLT lacks a data type set to be able to perform error detection. Clark felt that the world needs a "better XML specific language" and "XQuery is promising".

5) Avoid premature standardization.

Arguing that "having a standard is not always a good thing" and that "early standardization may cut off innovation" by preventing small organizations coming along with better solutions to the point where standards become "anti-competitive", Clark urged us to fight against premature standardization. And since "a lot of people accept standards uncritically", "people need to apply their critical faculties to standards". Clark also stated that "not everything needs to be a standard" giving the example of processing solutions which do not need to be exchanged and thus do not need to be standards. Clark reminded developers wanting to avoid "vendor lock-in" that open source is also a good solution.

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Re: Five challenges for XML (Jeff Lowery - 20:44, 19 Dec 2001)
When stating that there's no universal type system, it occurs to me that the field of mathematics ha ...
Re: Five challenges for XML (Eric van der Vlist - 12:48, 19 Dec 2001)
James made several different points about W3C XML Schema simple datatypes. The first was that no uni ...
Re: Five challenges for XML (Anthony B. Coates - 12:23, 19 Dec 2001)
In 1), I think you have a typo. It was the "data types" in general that I remember James referring ...
GCA should post the texts of this keynote (Gavin Bong - 03:43, 19 Dec 2001)
The summary by Eric is great but if only GCA could make available the speech in mp3 or text format. ...
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