[xquery-talk] Function for determining one XPath as subset of another
W.S. Hager
wshager at gmail.com
Tue Jan 26 09:06:44 PST 2016
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 <adam.retter at googlemail.com>:
> Any chance you could offer me an example? ;-)
>
> On 26 January 2016 at 16:40, W.S. Hager <wshager at gmail.com> 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 <adam.retter at googlemail.com>:
> >>
> >> 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
> >> _______________________________________________
> >> talk at x-query.com
> >> 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
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