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   Re: [xml-dev] XQuery and DTD/Schema?

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> [Simon St.Laurent]
> > At 02:30 PM 7/6/2002 -0400, Jonathan Robie wrote:
> > >For data that is physically represented as XML, there already *is* a
> > >layering - XML text is parsed to create an Infoset, which is validated to
> > >create a PSVI, which is mapped into the XML Query data model. Do you
> > >suggest a different layering? What layering would you prefer, and how
> > >would this relate to the XML Query data model and typed operatoins?
> >
> > That's easy.  Layer XML Query on the Infoset, drop the PSVI, and you have
> > half a chance of producing something likely to have a long and useful
> lifetime.
> >
> I'd like to suggest a different take on why there may have been such a hue
> and cry about XQuery/Xpath2/XML Schema.  I think it has a lot of explanatory
> power.  See what you all think.
> Up until recently, most experienced XML practitioners probably felt that
> they could write any part of the XML processing chain themselves if they had
> to or wanted to.  Anyone could write a parser (I'm not necessarily talking
> fact here, but perception), and most people probably though they could write
> an XPath processor if put to it.  XSLT would be harder, but still one or a
> small group could picture themselves doing it.  We have Saxon from Mike Kay,
> for example, and 4xslt from Uche's gang.
> Going along with this, if you needed, say, XPath for Ruby or Curl, you could
> imagine writing it if no one else got around to doing it.  In this lies a
> great sense of freedom.  You could do it yourself, and especially you could
> do it without needing the products of big companies.
> Now comes XML Schema.  This does not look like a one-person project (Yes, I
> know, XSV - I said it was about perception).  This is a big deal, if you
> could even understand the Rec well enough.  And to most people it probably
> does not seem like an interesting job, either.  To mix XML Schema into XPath
> for XPath2 also seems like a great burden.  XQuery seems too much to tackle,
> too.  SOAP toolkits - they are coming out of much bigger efforts.
> If this is close to the mark, the resentment and fear comes from a perceived
> withdrawal of the previous freedom.  Any unclear or complex feature of, say,
> XML Schema, will tend to trigger the reaction.  So no amount of explanation
> about any one issue can settle anything, which seems to be what we are
> seeing here.  The threads just keep circling around and repeating the same
> points.

I do think you really have something here, Tom.  In the XML world, it so often happens that the implementor is also the user that making life hard for the implementor is a significant problem.

I know that it probably helps explain the depth of my own annoyance.  Most of this second generation of XML specs is beyond my capacity to clearly understand, let alone implement on my own or in a small team, even though I think I carry a good deal of software experience and am a very productive programmer.

> Now personally, I do not see myself creating another RELAX NG validator.
> But the next best thing to actually being able to build something is for it
> to seem so clear and simple as to be quite understandable. So we keep
> hearing how simple and elegant RELAX NG is.  XML Schema can never be
> anywhere near as understandable.  If we can keep XPath2 simple - keep the
> @#$@! PSVI out - we can still feel like we can do it ourselves if we have
> to.

I just want to point out that Eric van der Vlist just implemented RELAX NG in about a week.  OK I lied.  He implemented RELAX NG + XVIF in about a week.  RELAX NG + extended processing features including regular fragmentations and the framework for binding them together.  All this single-handedly.

I think it illustrates your point marvelously.

> I am not suggesting that there are no technical or architecture issues that
> influence the discussion.  I am suggesting that there are hidden aspects to
> the debate, and theat they are fairly powerful.

Well, there is a lot hidden in this debate, and I think that big company ethos vs the open-source ethos (I already brought up the Cathedral and the Bazaar) is one that isn't brought up as often as I'd think in this context.  Perhaps everyone already knows these cards all to well.

Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Track chair, XML/Web Services One Boston: http://www.xmlconference.com/
The many heads of XML modeling - http://adtmag.com/article.asp?id=6393
Will XML live up to its promise? - http://www-106.ibm.com/developerworks/xml/library/x-think11.html


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