FDs and confluence

[Ross Paterson]

On Thu, Apr 13, 2006 at 12:07:53PM -0700, Iavor Diatchki wrote:
> On 4/12/06, Claus Reinke <claus.reinke at talk21.com> wrote:
> > that's why Ross chose a fresh variable in FD range position:
> > in the old translation, the class-based FD improvement rule no
> > longer applies after reduction because there's only one C constraint
> > left, and the instance-based FD improvement rule will only instantiate
> > the 'b' or 'c' in the constraint with a fresh 'b_123', 'b_124', ..,
> > unrelated to 'b', 'c', or any previously generated variables in the
> > constraint store.
> 
> I understand the reduction steps.  Are you saying that the problem is
> that the two sets are not syntactically equal?   To me this does not
> seem important: we just end up with two different ways to say the same
> thing (i.e., they are logically equivalent).

If c were mentioned in another constraint, they would not be equivalent.