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At 06:37 PM 6/7/2003 +1000, Rick Jelliffe wrote:
>From: "Jonathan Robie" <jonathan.robie@datadirect-technologies.com>
>
> > I consider W3C XML Schema too complex for its functionality, but the above
> > statement is really pretty ignorant.
"The above statement" was the implication that the W3C XML Schema people
were all dataheads. Michael and Henry are not dataheads, and they played a
major role.
> > Unless you mean it in the following way: any XML document can be processed
> > in ways that were once reserved for data stored in databases.
I did not mean to imply that W3C XML Schema is superior to RELAX-NG or even
particularly superior for DTDs when it comes to handling structured
documents. I do think that the Working Group took a requirement to support
the same idioms used for DTDs to structure documents, and we spent a fair
amount of time looking at the ways parameter entities are used in complex
document-oriented DTDs and trying to provide that functionality.
>Furthermore, the same kind of query could be done in XSLT and, indeed,
>in OmniMark or the various text processing languages people used with SGML.
>Extracting trees of information based on pattern-matching values has been
>around
>since markup languages were invented: auto-generated indexes for example.
>I don't really see Jonathan's point here.
Again, the context is important here. I was responding to the statement
that pull processing is not appropriate to documents. I was not claiming
that XQuery was the only language capable of doing this kind of processing,
merely that a language that is pull-oriented can be applied to documents.
> >From my POV, in my time as a member of the W3C XML Schemas WG, I cannot
>recall a *single* feature added to support publishing requirements (i.e.
>any additions
>that were not aimed at merely reconstructing DTDs or were also DBMS
>requirements).
First, I do think that it is important to distinguish publishing
requirements from general support for documents. For most of the life of
the Working Group, we really didn't have participation from people who
worked primarily in publishing.
I also agree that the focus was on ensuring that the document-oriented
idioms used in DTDs were still supported. I think that most of the Working
Group felt that DTDs work pretty well for documents.
>Such features could have included (but didn't) : being able to constrain
>mixed content
>data, co-occurrence constraints of various kinds, data-typing based on
>mapping idiomatic
>lexical forms to standard types, a module system (the trouble with
>"reconstructing what
>parameter entities do" is that, when the rubber hit the road with
>attempting to reconstruct
>what XHTML modularization did, WXS had not "reconstructed" all the bits
>of parameter
>entities used for versioning and customizing). Indeed, one pretty obvious
>way you
>can tell that WXS was not designed with publishing requirements to the
>fore was
>that it could have "reconstructed" SGML's features (#CURRENT etc) for
>non-resolved
>documents. Or provided link typing.
Personally, I wish that W3C XML Schema had fewer features rather than more.
A simple core module that could be extended with more specialized
validation, along the lines of Schematron, is far better than a monolithic
language with all of the features anyone might need in just about any domain.
>If you look at what was new in WXS: the type extension mechanism (by
>suffixation) is clearly
>too crippled for publishing requirements (you need to have a new element
>in the middle,
>you have to add it to the base schema then remove it again explicitly from
>all the derived
>schemas, or perhaps just lengthen the derivation chain with a new
>progenitor: yech),
>and xsi:nil, these are clearly not driven by publishing requirements.
I actually made proposals that would have allowed new elements to be added
to the middle. They were rejected because of their complexity - I didn't
find a simple way to do this.
>The most important question does not concern individual features, nor
>their negotiation,
>nor who were goodies and baddies, nor attacking these straw men who don't
>think
>queries are useful, etc, but the deeper question of whether type lattices
>are appropriate
>as the central organizing principle of new XML-family standards.
>
>That is a major architectural decision: for people who don't need type
>lattices, of course
>they will feel pissed off that the base-level of XML technology is being
>complicated (presumably
>Perry Mason could find the culprits quickly.) But from the baroque (SGML)
>to classical
>(XML) to primitivist (YAML) to conceptual art (WXS), why should everyone
>like the same art?
I think it is really important that new W3C standards support documents
validated by a DTD rather than a schema. The W3C currently has two schema
languages, and both XSLT and XQuery will support documents governed by
either. Note that the current Data Model has both Infoset-only and
PSVI-based mappings.
Jonathan
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