Hi Adam, I'm looking at the formal specification of xpath/xquery:
http://www.w3.org/TR/xquery-semantics It would really help to start with a function that implements the actual selection in steps. Do you know such a function? Thanks, Wouter Op dinsdag 26 januari 2016 heeft W.S. Hager <[email protected]> het volgende geschreven: > Not really, no. But my guess is that the path is not relevant, as its > steps simply contain variable names. The proof you want to have is a formal > one, and I think it doesn't have to do with the path expression, but rather > the formalism it implements. > > 2016-01-26 17:41 GMT+01:00 Adam Retter <[email protected] > <javascript:_e(%7B%7D,'cvml','[email protected]');>>: > >> Any chance you could offer me an example? ;-) >> >> On 26 January 2016 at 16:40, W.S. Hager <[email protected] >> <javascript:_e(%7B%7D,'cvml','[email protected]');>> wrote: >> > Hi Adam, >> > >> > Perhaps it helps to start with rewriting the xpath expressions as pure >> > lambda expressions. Maybe that way you could apply lambda calculus? >> > >> > Cheers, >> > Wouter >> > >> > 2016-01-26 17:26 GMT+01:00 Adam Retter <[email protected] >> <javascript:_e(%7B%7D,'cvml','[email protected]');>>: >> >> >> >> 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 >> >> _______________________________________________ >> >> [email protected] <javascript:_e(%7B%7D,'cvml','[email protected]');> >> >> http://x-query.com/mailman/listinfo/talk >> > >> > >> > >> > >> > -- >> > >> > W.S. Hager >> > Lagua Web Solutions >> > http://lagua.nl >> >> >> >> -- >> Adam Retter >> >> skype: adam.retter >> tweet: adamretter >> http://www.adamretter.org.uk >> > > > > -- > > W.S. Hager > Lagua Web Solutions > http://lagua.nl > -- W.S. Hager Lagua Web Solutions http://lagua.nl
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