Re: object algebra

"Neo" <neo55592_at_hotmail.com> wrote in message news:4b45d3ad.0402282053.5107b3e0_at_posting.google.com...
> > > Given EyeColor = {red, brown, NOT_APPLICABLE}
> > > Given the table:
> > > Person EyeColor
> > > ------ --------------
> > > Mary NOT_APPLICABLE
> > > Bob NOT_APPLICABLE
> > >
> > > Then, Mary.EyeColor equals Bob.EyeColor leading an AI[type] program to
> > > conclude that Mary and Bob have the same EyeColor.
> >
> > All of Bob's eyes have the same color as all of Mary's eyes.
> > What is the problem?
>
> This exemplifies Date's observation on p586: "3VL suffers from the
> very serious ("showstopper") problem that it does not match reality -
> that is, results that are correct according to 3VL are sometimes
> incorrect in the real world".

But it *does* match reality. If Bob has no eyes, and Mary has no eyes, then *in reality* all of Bob's eyes have the same color as Mary's eyes. The model and the reality match perfectly.

And again, there is no 3VL here.

Marshall Received on Sun Feb 29 2004 - 08:01:31 CET