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

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Actually i had the opposite question. Do we know of any work where XSLT has worked as a query language for database and the optimizations that have been done?
Or put another way is there an XSLT processor [or atleast a dumbed down XQuery equivalent processor] that has acted as a query engine?
I think that would be of immense interest!
My suspicion is it is early days either ways... but given the amount of investment the database community has placed on query optimization - I am guessing it will be easier to adapt those techniques for XQuery than it is for XSLT; but then again that is just my guess:-)

Dare Obasanjo <dareo@microsoft.com> wrote:
Do you have a list of the significant optimizations that can be made in XQuery that can't be done in XSLT?

To error is human, to forgive is against department policy.      

This posting is provided "AS IS" with no warranties, and confers no rights.


From: Prakash, Prakash Yamuna, Yamuna [mailto:techpy@yahoo.com]
Sent: Monday, December 13, 2004 2:19 PM
To: Liam Quin
Cc: XML Developers List
Subject: Re: [xml-dev] What niche is XQuery targeting?

Taken off in terms of wide acceptance - we wouldn't be having this discussion otherwise.
Definitely XQuery does not assume an XML database but if you look at the arguments in XQuery vs. XSLT - one (me) definitely comes off with a feeling that optimization is the key.
If so, I humbly submit that XML databases is the best bet as to where XQuery is likely to succeed. Perhaps reporting too...
If optimization is taken out of the picture - lot of things start falling apart for XQuery in my mind. Please see http://lists.xml.org/archives/xml-dev/200102/msg00483.html

Liam Quin <liam@w3.org> wrote:
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.

We'll see.


Liam Quin, W3C XML Activity Lead, http://www.w3.org/People/Quin/

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