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

[W.S. Hager]

Here's the entry on steps:

http://www.w3.org/TR/xquery-semantics/#id-axis-steps

I missed it before. To be continued I guess. I'd love the idea of a sound
formal proof.

Op dinsdag 26 januari 2016 heeft W.S. Hager <wshager at gmail.com> het
volgende geschreven:

> 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
> <javascript:_e(%7B%7D,'cvml','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>:
>>
>>> 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
>>
>
>
> --
>
> W.S. Hager
> Lagua Web Solutions
> http://lagua.nl
>
>

-- 

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