RE: XQuery -- Reinventing the Wheel?

[Evan Lenz <elenz@xyzfind.com>]

Michael Rys wrote:
> Don't get me wrong: For data-driven transformations XSLT's rule driven
> approach is great. The only problem is that have not yet seen a high
> performance/highly scalable engine for rule-based engines (and
> projects such
> as the ICSI project on a highly-parallel rule inference engine
> don't count,
> they normally test the boundary of hardware (cost)) that can compare to a
> algebra-based query engine with optimizer.

I want to address this in a separate post, because I don't want my opinion
here to muddy my larger argument, which is that the XML transformation and
XML query languages should build from a common semantic and syntactic base.

Disregarding performance issues, XSLT template rules work beautifully for
XML, and I think they would work beautifully over collections of XML
documents. While making implementors happy, it will be sad to see a stunted
specification prevent anyone from trying to implement fast rule-based XML
query engines... or even slow ones that work.

Consider the following truths:

*No query language that's remotely powerful always performs well on every
possible query.

*There are certain queries that you shouldn't execute if you want speed.
These are documentable.

*There are also certain queries that get you what you want, even though you
know it will be costly.


So maybe someone has tried to implement something like XSLT's template rules
over a large data set, and they've never succeeded in producing a scalable
result. I'm still sad to see it thrown out so early. It seems too early.

Evan Lenz
XYZFind Corp.