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Re: Level 3 XPath doesn't feel right

From: Ray Whitmer <rayw@netscape.com>
Date: Fri, 01 Nov 2002 04:48:08 -0800
Message-ID: <3DC27808.4030607@netscape.com>
To: www-dom@w3.org

Joseph Kesselman wrote:

>On Tuesday, 10/29/2002 at 09:11 EST, "Dominic Chambers" 
><dominic.chambers@bigfoot.com> wrote:
>  
>
>>1. XPathEvaluator should be implemented by objects  that currently 
>>    
>>
>implement 
>  
>
>>Node, not
>>    Document, since you need to have  the context node anyway, and 
>>node.evaluate(expr),
>>    is cleaner and more OO than  document.evalute(expr, node).
>>    
>>
>
>In isolation, I would agree with you. However, I believe the intent was to 
>allow stand-alone implementations of the XPathEvaluator which could be 
>combined with DOMs that don't directly support this feature; the process 
>of obtaining the evaluator would be different but thereafter the code 
>would be the same, minimizing the multi-pathing/recoding needed to go from 
>built-in to stand-alone implementations or vice versa. If we accept that 
>goal, we do need to be able to pass the node explicitly.
>  
>
I agree.  If there were only ever going to be one implementation made 
available by the DOM implementor, then putting it on the Node would make 
a lot of sense.  But there may even be multiple evaluators available, 
used for different purposes, on the same set of nodes.

The implementation is only available on Document so that applications 
without a place to get one that is more specific to their requirements 
can get a default implementation in a platform-independent way.

It is quite likely that one system processing a DOM hierarchy may rely 
on an evaluator supporting a specific set of extension functions, and 
some other implementation may have a different set of functions 
available.  Marrying it to the node would make it quite difficult to 
switch to a different evaluator implemented for some other purpose such 
as a version of XSLT when processing in a different environment.

Ray Whitmer
rayw@netscape.com
Received on Friday, 1 November 2002 07:48:56 GMT

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