> > 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] > <mailto:[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] > <mailto:[email protected]>>: > > > On 27 Jan 2016, at 12:54, W.S. Hager <[email protected] > > <mailto:[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 <http://lagua.nl/> > > > > -- > W.S. Hager > Lagua Web Solutions > http://lagua.nl <http://lagua.nl/>
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