Indeed, the expressions should terminate. 2016-01-27 11:11 GMT+01:00 Pavel Velikhov <[email protected]>:
> > > 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 <[email protected]>: > >> 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 <[email protected]>: >> >>> >>> > On 27 Jan 2016, at 12:54, W.S. Hager <[email protected]> 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 >> > > > > -- > > W.S. Hager > Lagua Web Solutions > http://lagua.nl > > > -- W.S. Hager Lagua Web Solutions http://lagua.nl
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