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Re: XPath and XPattern (was Re: More on tamingSAX)

• To: kjouk@y...
• Subject: Re: XPath and XPattern (was Re: More on tamingSAX)
• From: Uche Ogbuji <uche.ogbuji@f...>
• Date: Fri, 24 Dec 2004 10:28:49 -0700
• Cc: xml-dev@l...
• In-reply-to: <200412241618.32481.kjouk@y...>
• Organization: Fourthought, Inc.
• References: <E1ChXnb-0004PJ-00@u...> <200412241130.59409.kjouk@y...> <41CC2983.3020009@f...> <200412241618.32481.kjouk@y...>
• User-agent: Mozilla Thunderbird 0.9 (X11/20041127)

Kevin Jones wrote:

>On Friday 24 December 2004 14:36, Uche Ogbuji wrote:
>  
>
>>Kevin Jones wrote:
>>
>>Of course XPath is always streamable, if you have no
>>practical limitations (e.g. you're willing to store all
>>node data and implement unbounded look-ahead).  When
>>people speak of a "streamable subset", they mean a subset
>>that works practically with most streaming host
>>languages, meaning that these host languages should not
>>have to compromise too much memory or state complexity in
>>order to satisfy the scope of node requests from the
>>XPath subset.
>>    
>>
>
>Hi,
>
>I was probably being a little brief. I was not intending 
>just to comment that XPath was theoretically possible, but 
>the assumption you need a subset for this case may be 
>wrong. Taking the examples of storing all node data and 
>unbounded look-ahead, clearly neither of these are 
>requirements of streaming XPath, just features of some way 
>of implementing it.
>  
>

I think I've used some loose language of my own.  I tried to be a bit 
more scrupulous in my last post:

http://lists.xml.org/archives/xml-dev/200412/msg00655.html

Does the conceptualization I present at the end of that posting help 
clarify the idea of an "XPath subset friendly to SAX processors"?

>I would say that having written/supported one streamable 
>subset for a few years they never implemement enough. Some 
>of the harder features to implement in a streamable way are 
>just the ones that make XPath better than any old pattern 
>language, e.g. predicates as expressions.
>  
>

This is true, somewhat unfortunately.


-- 
Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Use CSS to display XML - http://www.ibm.com/developerworks/edu/x-dw-x-xmlcss-i.html
Full XML Indexes with Gnosis - http://www.xml.com/pub/a/2004/12/08/py-xml.html
Be humble, not imperial (in design) - http://www.adtmag.com/article.asp?id=10286
UBL 1.0 - http://www-106.ibm.com/developerworks/xml/library/x-think28.html
Use Universal Feed Parser to tame RSS - http://www.ibm.com/developerworks/xml/library/x-tipufp.html
Default and error handling in XSLT lookup tables - http://www.ibm.com/developerworks/xml/library/x-tiplook.html
A survey of XML standards - http://www-106.ibm.com/developerworks/xml/library/x-stand4/
The State of Python-XML in 2004 - http://www.xml.com/pub/a/2004/10/13/py-xml.html

• References:
  • RE: XPath and XPattern (was Re: More on taming SAX)
    • From: "Michael Kay" <mike@s...>
  • Re: XPath and XPattern (was Re: More on taming SAX)
    • From: Kevin Jones <kjouk@y...>
  • Re: XPath and XPattern (was Re: More on tamingSAX)
    • From: Uche Ogbuji <uche.ogbuji@f...>
  • Re: XPath and XPattern (was Re: More on taming SAX)
    • From: Kevin Jones <kjouk@y...>

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