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> Michael, you read a two years old version
of the paper, the one I was pointing to is the journal
(i.e. longer) and
newer version of it. The architectural main idea didn't change, but the numbers
are better (like any other new processor, the performance improves with 10%
per day, so it depends
what day of the week do you measure ...:-)
I read the version I could find! Is it worth paying $35 to
see the updated one? I did guess that your [BEA's!] numbers had almost certainly
improved in the meantime (Saxon's figures on XMark are about ten times better
than the ones you quoted).
By the way, the paper used a private benchmark to compare
XQRL and Xalan-J, and suggested it would be available on the web. Is
it?
Our major goals while designing this were:
-
build a full implementation for XQuery (I really mean 100%), not only a
"convenient" subset
- use streaming
- use lazy evaluation
As you
point out the interesting discussion is between pull and push streaming. There
are multiple
reasons we used pull, the main important ones being:
- we are
database people, so we grew up with the pull, iterator based evaluation of the
relational
database engines and
- it was harder to make push and lazy
evaluation work together
In XSLT 1.0 it was relatively easy to use pull for the
XPath reading, push for the XSLT writing. With the richer processing
model of XQuery and XSLT 2.0
this mixed approach is certainly much more difficult. In Saxon today, many
expressions can be evaluated in either pull or push mode, and the goal I'm
pursuing is to keep both, while reducing the number of push/pull conflicts. The
subject of a future paper perhaps.
There is a piece of good
work that compares push and pull XML processing, I am sure you'll enjoy it.
Well, it doesn't do much comparison, but it certainly makes
a push-based approach look delightfully easy. If only it were
true...
Michael Kay
"The
Joy of SAX"
Leonidas Fegaras (University of Texas at Arlington, USA)
Best
regards,
Dana
P.S.
It looks like I am doing more publicity now to BEA, when I'm not there
anymore:-)
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