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Re: XQuery and DTD/Schema?

• To: <xml-dev@l...>
• Subject: Re: XQuery and DTD/Schema?
• From: "Rick Jelliffe" <ricko@a...>
• Date: Wed, 3 Jul 2002 17:53:43 +1000
• References: <AOEKKCOOGNDOAHCLNEIFGELLDCAA.mike@w...>

From: "Michael Fitzgerald" <mike@w...>


> Good question. I have another. My apologies if it has already been clearly
> answered but I don't think it has.
> 
> I am looking for a technical, non-political reason why RELAX NG has been
> brushed aside by XQuery.
> 
> Any XQuery people want to speak to that?

I am certainly not an XQuery person, but "brushed aside" is not accurate.

XQuery was under way (in some form) before RELAX was developed, and
certainly before RELAX NG.  Just as RELAX came too too late to
influence the fundamental stages of WXS, so RELAX NG is too
late to influence the fundamental stages of XQuery.

Furthermore, the point of XQuery (rightly or wrongly: depends on your use 
cases and your vision of the Web) is to make use of types: RELAX NG has been
explicitly not about types in that same way.  So there is a technical impediment
too.

But now RELAX NG is out, and clearly viable and attractive, there are different
dynamics.  First, the RELAX NG people are, I think, looking at various ways
that RELAX NG could be more useful for queries. Second, there is discussion
at the W3C to disconnect XQuery from WXS validation (see Tim Bray's
comments on the TAG public list).  Such a Type-augmented Infoset (TAI rather
than a PSVI) would still be based on the categories established in WXS,
but it would be clearer that the augmentations could come from different
schema languages. I expect that this is the way things will with XQuery
and subsequent revisions of WXS.   

So we shouldn't see XQuery per se as a conspiracy against RELAX NG.
However, the general idea that an XPath 2 (in particular) implementation
would require a WSX validator does unfairly privilege WXS (and a TAI),
and that is the wrong direction. 

Cheers
Rick Jelliffe

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