Release of the GCX XQuery EngineQ

[Stefanie Scherzinger]

> In order to be a little more concrete, I talked with Marc about some
> comparisons we did internally between GCX and DataDirect XQuery. I think
> the results fall out roughly as follows:
>
> - Our XMark performance results are broadly similar to those of GCX for
> our currently released software. The upcoming DataDirect XQuery 3.0 will
> be markedly faster in some cases - for instance, for one XMark query, we
> finished more than 100 times faster.

I assume that the one XMark query where you outperform us in runtime
is the one with the join, where we still only have a naive nested-loop
implementation.

> - Our memory usage was similar for many queries, worse for some, and
> better for others.

This is very interesting, do you think we could include experiments
with your product on our benchmark site?

> As Marc indicated, we support both document projection and streaming (as
> described in A. Marian and J. Simeon, "Projecting XML Documents", Proc.
> VLDB 2003, a really cool and useful paper).

Out of curiosity - does your projection strictly adhere to the
technique described in this paper? GCX projection is similar, but it
is also capable of omitting inner nodes. For instance, to project for
the path //a in <x><b><a/></b></x>, the x- and b-labeled nodes are not
buffered by GCX. Interestingly, this can really make a difference when
projecting very large XML documents, even if they are shallow.

Steffi