luque@info.ucl.ac.be (Luis Quesada) writes:
> > * it doesn't actually do what you set out to do, which was to get rid
> > of sibling guards once you have decided for one of them. In the
> > direction cond->or things are ok, but in the direction or->cond,
> > they are not. Suppose you explicitly decide C=2, this does not
> > cause the cond to commit to the 2nd alternative... and this brings
> > us to the last and damning problem:
>
> This is not totally true.
yes it is, simply because propagation is not complete. Don't be
misled by examples where there are only basic constraints; think of
non-basic constraints (i.e. propagators).
> > * it has confluence problems.
> [...]
> Agree, but I wonder whether this indeed happens in a real scenario....
it's not a question of likelihood, but of semantics. A constraint
should have well defined logical semantics. Your constraint, however,
has the property that for the same variable assignment it is sometimes
entailed and sometimes disentailed.
There are many applications where non-confluence is perfectly
acceptable, formulating and solving constraint satisfaction problems
is not one of them.
Cheers,
-- Dr. Denys Duchier Denys.Duchier@ps.uni-sb.de Forschungsbereich Programmiersysteme (Programming Systems Lab) Universitaet des Saarlandes, Geb. 45 http://www.ps.uni-sb.de/~duchier Postfach 15 11 50 Phone: +49 681 302 5618 66041 Saarbruecken, Germany Fax: +49 681 302 5615 - Please send submissions to users@mozart-oz.org and administriva mail to users-request@mozart-oz.org. The Mozart Oz web site is at http://www.mozart-oz.org/.