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On Mon, Dec 13, 2004 at 01:37:30PM -0800, Prakash, Prakash Yamuna, Yamuna wrote:
> Perhaps XQuery has not taken off because it was designed primarily
> as query language for an XML database? If we look back at the
> justifications for XQuery - optimization stands out as primary reason.
It's not clear to me that it "hasn't taken off". There are a couple
of dozen implementations in various staets of completeness listed from
http://www.w3.org/XML/Query so I think it's fair to say XQuery is
far from still-born.
Furthermore, it's not correct to say it assumes an XML database.
XSLT and XQuery both operate over instances of the XPath 2.0 Data Model,
and such instances can be provided by XML documents (the most common
use case for XSLT today), by projections of relational databases, by
XML-native databases, or by entirely different systems.
Time will tell how widely used XML Query will be.
My own guess would be that it'll start out replacing (or subsuming)
middleware -- the ability to do, in effect, joins between data from
disparate sources, such as two SQL databases, some XML documents and
perhaps an RDF store, generating an XML report directly, is something
difficult to do with other technologies without getting deeply tied
to a single vendor. Perl can do this, but with a lower level of
programming that's relatively fussy.
Liam Quin, W3C XML Activity Lead, http://www.w3.org/People/Quin/