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From Simone Gianni <simo...@apache.org>
Subject Re: XInclude optimization
Date Mon, 23 Nov 2009 17:52:29 GMT
Hi Simone and Sylvain,
aren't XSLT transformers already SAX/Xpath optimized? I mean, an XSLT 
containing an XPath expression and used in a SAX context, isn't already 
able to resolve the XPath while keeping buffering at the minimum possible?

I can clearly remember that there has been a lot of work about this in 
Xalan and other XSLT engines, and also how a complex XPath expressions 
could change the performance of a transformation because of increased 
buffering.

In that case, maybe, instead of reinventing it, it should be possible to 
delegate the "transformation" (extraction of a fragment from the entire 
XML stream) to an XSLT processor. The simplest way could be to generate 
an XSLT on the fly :) .. the correct way would be to use the 
[Xalan|Saxon|any other] internal APIs to perform the XPath resolution. 
In both cases, it will be faster than transforming to DOM.

Simone


Simone Tripodi wrote:
> Hi Sylvain,
> indeed, that's yet another exception I didn't think, thanks for your
> clarification!!!
> Bonne journée, a bientot ;)
> Simo
>
> On Mon, Nov 23, 2009 at 8:28 AM, Sylvain Wallez <sylvain@apache.org> wrote:
>   
>> Jos Snellings wrote:
>>     
>>> Hmmm, I guess the XPath expression is known before the parsing begins?
>>> I remember I have done a similar thing, where a chunk had to be isolated
>>> from a document that came by via a SAX stream, but here the xpath
>>> expression was something like: "/element1/element2[@id=somenumber]".
>>>
>>> Theorem: any XPath expression can be evaluated with a SAX filter.
>>> Proof?
>>> Do you know some exceptions?
>>>
>>>       
>> What about this one : //foo[bar[position() = 3]//baz], find all elements
>> "foo" whose 3rd "bar" child has a "baz" descendent element.
>>
>> This requires to buffer the contents of every "foo" element to inspect their
>> chidren sub-tree.
>>
>> Sylvain
>>
>> --
>> Sylvain Wallez - http://bluxte.net
>>
>>
>>     
>
>
>
>   


-- 
Simone Gianni            CEO Semeru s.r.l.           Apache Committer
http://www.simonegianni.it/


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