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

[Pavel Velikhov]

> 
> Or simplified: is the set selected by p1 equal to the set selected by p2?

If we allow p1 and p2 to be arbitrary XQuery path expressions, then its undecidable.
I can reduce the halting problem of Turing machines to this test.

> 
> 2016-01-27 11:09 GMT+01:00 W.S. Hager <wshager at gmail.com <mailto:wshager at gmail.com>>:
> Isn't the constraint in this case the test: is p2 a subset of p1?
> 
> 2016-01-27 11:04 GMT+01:00 Pavel Velikhov <pavel.velikhov at gmail.com <mailto:pavel.velikhov at gmail.com>>:
> 
> > On 27 Jan 2016, at 12:54, W.S. Hager <wshager at gmail.com <mailto:wshager at gmail.com>> wrote:
> >
> > Can't we formally proof something as obvious Adam's case?
> 
> In Adam’s case we want to test whether path expression p1 subsumes path expression p2.
> If we don’t put any conditions on p1 and p2, the problem is undecidable: p1 and p2 may include
> function calls, so the expressive power of p1 and p2 are that of a Turing Machine.
> 
> 
> 
> -- 
> W.S. Hager
> Lagua Web Solutions
> http://lagua.nl <http://lagua.nl/>
> 
> 
> 
> -- 
> W.S. Hager
> Lagua Web Solutions
> http://lagua.nl <http://lagua.nl/>

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