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Subject: AW: AW: [xsl] why is "(chapter//footnote)[1]" illegal? From: Markus Abt <abt@xxxxxxxx> Date: Sat, 23 Aug 2003 22:36:11 +0200 |
well, > ---------- > Von: Robert P. J. Day > Gesendet: Samstag, 23. August 2003 17:42 > An: 'xsl-list@xxxxxxxxxxxxxxxxxxxxxx' > Betreff: Re: AW: [xsl] why is "(chapter//footnote)[1]" illegal? > > On Sat, 23 Aug 2003, Markus Abt wrote: > > > Hi Robert, > > > > a pattern (p.443) is a path expression, but not every > > path expression (.p408) is a valid pattern. > > well, since mom is still putzing around in the kitchen and not > ready to go shopping yet, i'll expand on this a bit more. > > i'm aware (kay, p. 430 -- a book that is getting mighty dog-eared by now) > that "every pattern is a valid XPath expression, but not every valid XPath > expression is a valid pattern." fair enough -- kay uses the example of > "2+2" as an expression that makes no sense as a pattern. > > but that example is pretty obvious -- "2+2" *clearly* can't be > interpreted as a pattern. it's not so obvious why the following > set of expressions can or can't be used as patterns: > > (chapter/para)[1] yes (kay, 408) > (chapter//footnote)[1] no (kay, 443) > ($chapters//diagram)[1] yes (kay, 355) (chapter/para)[1] no (chapter//footnote)[1] no ($chapters//diagram)[1] no All three can not be used as patterns. > it's not at all clear *intuitively* why the first and third expressions > are acceptable patterns, while the second isn't. and it's not because > that 2nd expression couldn't be interpreted unambiguously, AFAICT. > > after i take a closer look at the actual rules for acceptable patterns, > i'm sure i'll understand it. but i just won't like it. :-) > > rday > Markus __________________________ Markus Abt Comet Computer GmbH http://www.comet.de XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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RE: AW: [xsl] why is "(chapter//foo, Michael Kay | Thread | Re: AW: AW: [xsl] why is "(chapter/, Robert P. J. Day |
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