RE: Nate's objections to Motion 42
Nate Hayes wrote:
> ... These two decorations can be merged into a single "not defined"
> decoration (ndf), since both
> sqrt([-2,-1]) and text2interval("friedchicken")
> are "not defined," just as you have said.
In other words, there should (in Nate's view) be NO DIFFERENCE between
text2interval("friedchicken") and text2interval("Empty"). Neat -- we
don't need to reserve a name for Empty. Another simplification.
However, Nate DOES seem to want a difference between
sqrt(Empty) = Empty_EIN
and
sqrt([-2,-1]) = Empty_NDF
Go figure!
Ok, let's be serious now.
I suppose the difference between friedchicken and Empty is that the
former leads to a bad Empty_NDF and the latter leads to a good Empty_emp
(or, if we drop _emp, Empty_trv). I believe it is imperative that we
preserve the distinction between good Empty (e.g. resulting from an
intersection, or from a constraint having no solutions) and a bad Empty
(possibly not an interval at all). If we drop both _ill and _emp, we
are in deep doodoo. Unfortunately I'm not convinced yet that Nate's EIN
is a conflict-free solution.
The reason I see a difference between sqrt[-2,-1] = Empty_ndf and
text2interval("friedchicken") = Empty_ndf is that the former can
arise legitimately when domains are split up into pieces, and it
makes sense to track what is happening to the pieces, whereas the
latter is definitely Not an Interval and it should be possible to
be alerted to its occurrence as soon as practical.
Michel.
---Sent: 2013-02-11 21:14:41 UTC