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Re: Action Item: rework 4.1.4 (cf. http://www.w3.org/2007/05/30-i18nits-minutes.html#action06)

From: Felix Sasaki <fsasaki@w3.org>
Date: Fri, 15 Jun 2007 06:09:28 +0900
Message-ID: <4671AE88.40200@w3.org>
To: Jirka Kosek <jirka@kosek.cz>
CC: "Lieske, Christian" <christian.lieske@sap.com>, public-i18n-its@w3.org

Jirka Kosek wrote:
> Felix Sasaki wrote:
>
>   
>> The best free tutorial I know is available at ZVON
>> http://www.zvon.org/xxl/XPathTutorial/General/examples.html .
>>
>> The difference between two XPath expressions at the end of your proposal
>> is that //del/descendant-or-self::*/@* has 3 steps
>> //del
>> //descendant-or-self::*
>> /@*
>>
>> whereas //@*[ancestor::del] has only one step and a predicate
>> //@*
>> [ancestor::del]
>>
>> which is less effort to compute. Maybe we should add such an explanation
>> to the example (without the detailed steps).
>>     
>
> I would prefer not adding such explanation into example. The problem is
> that it is very hard to compare efficiency of two XPath expression as it
> depends on particular XPath implementation used. Clever optimizer can
> automatically rewrite former expression into later. Moreover in some
> expressions efficiency could depend on frequency of particular elements
> and attributes that are evaluated in XPath expression.
>   

all good points. So let's drop the mentioning of specific XPath expressions.

Felix
Received on Thursday, 14 June 2007 21:09:38 GMT

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