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. FelixReceived on Thursday, 14 June 2007 21:09:38 GMT
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