W3C home > Mailing lists > Public > public-i18n-its@w3.org > April to June 2007

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

From: Jirka Kosek <jirka@kosek.cz>
Date: Thu, 14 Jun 2007 14:28:54 +0200
Message-ID: <46713486.4090202@kosek.cz>
To: Felix Sasaki <fsasaki@w3.org>
CC: "Lieske, Christian" <christian.lieske@sap.com>, public-i18n-its@w3.org
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.

  Jirka Kosek      e-mail: jirka@kosek.cz      http://xmlguru.cz
       Professional XML consulting and training services
  DocBook customization, custom XSLT/XSL-FO document processing
 OASIS DocBook TC member, W3C Invited Expert, ISO JTC1/SC34 member
Be in, register for XML Prague 2007 today! http://www.xmlprague.cz

Received on Thursday, 14 June 2007 12:28:43 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 20:43:09 UTC