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RE: Datatypes vs anarchy
- From: "Simon St.Laurent" <firstname.lastname@example.org>
- To: Michael Champion <email@example.com>,xml-dev <firstname.lastname@example.org>
- Date: Tue, 13 Mar 2001 20:07:34 -0500
At 06:14 PM 3/13/01 -0500, Michael Champion wrote:
>In my very humble but biased opinion, DOM Level 3 is doing the "right thing"
>in that the content models and validation component is a separate, optional
>module. Implementers can choose to ignore it, and consumers can test for its
>support and either use it, or not use it. Nothing in the rest of the DOM
>depends on the CM module. It is not easy to carve out independent API
>modules from the alleged "layers" of XML-related specs, but the DOM WG tries
>very hard to do so.
That's an incredibly tough job, and I'm really impressed by the
approach. I thought the modules thing was a bit weird when I first saw it
(yet another side of complexity?), but I've really come to like it.
>In the W3C Schema spec, data types are an integral part of the overall spec
>(the "part 1" and "part 2" distinction does not reflect any explicit
>modularization). The PSVI is not (as far as I can find) explicitly, much
>less modularly, defined. This means that XPath 2.0, XSLT 2.0 and XQuery
>depend on the Schema spec as a whole rather than being layered on the
>PSVI/datatypes. It is true that a consumer of XPath 2.0/XSLT 2.0 need not
>actually define a schema to write queries or stylesheets, but (as near as
>one can tell from the Requirements so far), implementers and explainers of
>XPath 2.0 will have to incorporate implementations/explanations of XML,
>namespaces, the PSVI, and the W3C Schema datatypes before even getting
>around to XPath. The opportunities to confuse the uninitiated here are
>enormous, exponentially more so than in the good ol' days of XML 1.0's
Yep! And you didn't even need to point out the options in the
non-validating side of XML processing...
>While I'm on a rant ... we don't simply have
>"well-formed/valid/schema-valid" layers of XML processing. We have (and this
>is not at all an exhaustive list) well-formed, well-formed-DTD-aware,
>DTD-validating, namespace-aware, namespace-aware-DTD-aware, (but NOT
>namespace-aware-DTD-validating), schema-validating (implies
>namespace-aware), schema-validating-DTD-aware, and (God help us)
>DTD-validating-schema-validating ... Then we have the fact the the InfoSet
>is really just a common vocabulary for implementers, and that the DOM,
>Xpath/XSLT, and XQuery all implement their own flavor of the thing. I'm
>sorry, but I'll bet it would be hard to find a rational person coming in
>from the outside, trying to make sense out of this, who wouldn't use some
>synonym for "entangled" to describe it. And then there are the (ahem)
>"colorful" descriptions of all this elegance over at xmlbastard.com, if you
>think that *I* am being a bit unfair :~)
Henry Thompson did cook up some very nice acronyms for some of these a
couple of weeks ago that were pretty colorful themselves.
>The DOM is far from perfect, but uses two principles that the rest of the
>W3C doesn't seem to take very seriously: Levels of the Recommendation come
>out when there is "minimal progress to declare victory" and the spec is
>built out of independent modules.
Sounds like an incremental approach, and one that helps people get their
I had a fun conversation with someone last week who'd started out trying to
read the entire DOM spec and was really desperately unhappy at
first. (It's a lot of paper!) Then he realized that he only needed about
100 pages total, and that the rest was genuinely for other people. That
made a big difference. I'm not sure he'd be happy to find an extra 200-400
pages becoming important to his work if he found himself processing
documents which were really about the PSVI...
Those who process the documents often have to contend with the expectations
of those who write them, for business reasons if nothing else.
Simon St.Laurent - Associate Editor, O'Reilly and Associates
XML Elements of Style / XML: A Primer, 2nd Ed.
XHTML: Migrating Toward XML
http://www.simonstl.com - XML essays and books