Re: Cyclic Classes/Properties

On Fri, 11 May 2001, Enrico Franconi wrote:

> If you have a propositionally closed representation language, then
> having a not-strict-sub-class-of allows you to have the
> strict-sub-class-of as well. So there is NO trading inferability
> against expressiveness.

You're obviously correct. An obvious follow-up question is: Why doesn't
daml do it this way? Or does it, but I'm not able to see it (because I
might not be able to recognize a "propositionally closed representation
language" when I see it ;).

> This is how you could represent your example:
> 
> Introduce first a freshly new primitive class "non-sub-title".
> Add the following axioms:
> 
> sub-title is-a-not-strict-sub-class-of title.
> title is-a-not-strict-sub-class-of (sub-title or non-sub-title).
> non-sub-title is-a-not-strict-sub-class-of ((not sub-title) and title).
> 
> This implies:
> sub-title is-a-strict-sub-class-of title
> 
> cheers
> -- e.

Have a nice weekend

Sigge