[xquery-talk] General comparisons of speed of xquery vs. xslt

[Daniela Florescu]

> (b) with in-memory transformations there is no intrinsic reason why 
> XQuery
> should be faster than XSLT

Michael,

I think I disagree with this statement. This might be due to the fact 
that
I understand XQuery much better then I do understand XSLT, but here is
my rationale anyway.

Most XQuery code rewriting rules that we apply in the BEA 
implementation require
serious dataflow analysis (i.e. how is the data flowing through 
expressions, where is the
data coming from and where is it going), similar in spirit with the way 
all modern compilers do.

Trivial examples of code rewriting rules that require dataflow analysis 
are
eliminating the unnecessary sorts and duplicate elimination, 
transforming backwards
navigation into forward navigation, introducing parallelism  and 
asyncronicity, etc, but there
are many, many others.

Moreover, we are building a streaming XQuery engine. Of course, not all 
queries can be
executed in a purely streaming fashion. We use the same dataflow 
analysis to
detect and minimize the need for materialization, which is essential 
for query performance.

Now it seems to me that this dataflow analysis is easier to do in 
XQuery (through expressions)
then in XSLT (through templates).  Knowing XSLT much better then I do, 
what is your take on this?
Are there any XSLT implementations that do dataflow analysis for 
optimization ?

Best regards,
Dana

P.S. A while ago we wrote a paper describing our streaming XQuery 
implementation
	• 	Daniela Florescu, Chris Hillery, Donald Kossmann, Paul Lucas, Fabio 
Riccardi, Till Westmann, Michael J. Carey, Arvind Sundararajan, Geetika 
Agrawal:
The BEA/XQRL Streaming XQuery Processor. VLDB 2003: 997-1008
http://www-dbs.informatik.uni-heidelberg.de/publications/index.shtml
A better version will appear in VLDB Journal soon.

And by the way, in this paper we did compare our XQuery implementation 
with an XSLT implementation.
While doing so, we did translate XMark in XQuery. If there is some 
demand, we can spend some time,
polish those queries and publish them in an open forum somewhere.




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