[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Function for determining one XPath as subset of a
I've always been a little frustrated that I rely heavily on equivalences like preceding::x === ancestor-or-self::*/preceding-sibling::*/descendant-or-self::* without having what I would consider a formal proof. Michael Kay Saxonica > On 26 Jan 2016, at 16:15, Adam Retter adam.retter@xxxxxxxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > Given two simple XPaths, say: > > 1. //w > > 2. /x/y/z/w[@a = 'v'] > > As a human I can very easily tell without evaluating the expressions > that (2) will return a subset (or the same set) of the results that > (1) would return *should* they both be evaluated. > > My goal here is given any two simple arbitrary XPaths expressed as > strings, and without evaluating them against a context, to determine > whether one would return a subset of the results of the other. > > I wondered if there might be an algorithm or library that someone > already had or has written which might be able to give me the answer? > > I realise that I can only probably cover a subset of XPath itself, but > it is only the path steps with predicates which I am interested in. > > Ideally I am looking for something in Java. > > -- > Adam Retter > > skype: adam.retter > tweet: adamretter > http://www.adamretter.org.uk
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