[xquery-talk] Function for determining one XPath as subset of another

[W.S. Hager]

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 <wshager at gmail.com> 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 <adam.retter at googlemail.com
> <javascript:_e(%7B%7D,'cvml','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
>> <javascript:_e(%7B%7D,'cvml','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
>> <javascript:_e(%7B%7D,'cvml','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 <javascript:_e(%7B%7D,'cvml','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
>


-- 

W.S. Hager
Lagua Web Solutions
http://lagua.nl
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