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   RE: [xml-dev] What niche is XQuery targeting?

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  • To: "Ronald Bourret" <rpbourret@rpbourret.com>,"XML Developers List" <xml-dev@lists.xml.org>
  • Subject: RE: [xml-dev] What niche is XQuery targeting?
  • From: "Dare Obasanjo" <dareo@microsoft.com>
  • Date: Tue, 14 Dec 2004 08:05:14 -0800
  • Thread-index: AcThoPXzRCdyytdRTt6MnNQHZqSC4wAVOngq
  • Thread-topic: [xml-dev] What niche is XQuery targeting?

People keep saying this as if it so trivial. Basically all you've described is what Crystal Reports does today but you've substituted SQL for with XQuery. However due to the fact that XQuery + XSD have a significantly different type system from your underlying relational or other data stores this causes for interesting impedence mismatch when performing queries. 
Heck, the XML Web Services folks are choking on figuring out how to map XSD to variables in OO languages let alone how to map an entire query language with operator precedence rules, collation rules, sort order, etc from one to another. 
Treat everything as a virtual XML document then query it with XQuery is one of those ideas that sounds good on paper until you actually start trying to implement it or use it. 
Eat right, Exercise, Die anyway.   


From: Ronald Bourret [mailto:rpbourret@rpbourret.com]
Sent: Mon 12/13/2004 9:46 PM
To: XML Developers List
Subject: Re: [xml-dev] What niche is XQuery targeting?

Treat each (non-xml) data source as one or more virtual XML documents
and write your query accordingly. This is definitely being done today.
Remember, performance is relative -- for example, queries in data
warehouses are usually slower than in transactional databases -- and
slow performance is better than no application at all, which is often
the case with these sorts of applications.

-- Ron

Dare Obasanjo wrote:
> Huh? Exactly how does XQuery allow me to join data between disparate
> sources such as two SQL databases, some XML documents and an RDF store
> [in any sort of performant manner]?

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