Re: An alternative to possreps

On Jun 7, 9:49 pm, Bob Badour <b..._at_badour.net> wrote:
> David BL wrote:
> > On Jun 6, 9:26 pm, Erwin <e.sm..._at_myonline.be> wrote:
>
> >>On 31 mei, 11:54, David BL <davi..._at_iinet.net.au> wrote:
>
> >>>Is there anything in TTM that prohibits one from making every type a
> >>>dummy type? Would that make it essentially the same approach which
> >>>I've described?
>
> >>Not "in TTM". What prohibits this is "reality", I'd rather say.
>
> >>If you're interested in a subset of T, then you can't define this
> >>subset by means of UNIONs involving T.
>
> > Yes, but that is not a problem. Let Ellipse be a "dummy type". If
> > you're interested in a subtype Circle of Ellipse then you can simply
> > declare Circle as another dummy type. I'm assuming you can declare
> > subtype relationships between dummy types. In my approach you use
> > these declarations:
>
> > type Ellipse;
> > type Circle;
> > Circle isa Ellipse;
>
> > I consider types like Circle and Ellipse to be defined by their
> > operators. In that sense there is no problem treating all types as
> > "dummy types".
>
> Either the operators define the equivalent of possreps or the type model
> doesn't really describe ellipses and circles. So what are you trying
> to achieve?

I'm suggesting the operators define the equivalent of possreps. Possreps are redundant.

The equality operator has a role to play in this. The possrep constraint which specifies which representations of ellipses are circles is instead defined indirectly by the equality operator (which defines which representations of ellipses are equal to some representation of a circle). Received on Wed Jun 08 2011 - 03:55:08 CEST