Re: SUO: Re: W3C approves RDF and OWL as recommendations
John,
I guess we disagree on this point. One clarification though is that I
didn't say Guarino/Welty's notion wasn't "completely strict". In fact it
is for them. I take a less strict view than they do. Not all notions in
life are binary.
Adam
At 01:17 PM 2/16/2004 -0500, John F. Sowa wrote:
>Adam,
>
>AP> This issue has been discussed at some length before.
> > Guarino/Welty argue for the same distinction even more
> > strongly than I with their notion of 'identity'.
> > When a class hierarchy is non-monotonic it does make
> > reasoning problematic.
>
>Who said anything about nonmonotonic logic? If you have
>a parentOf relation, the set of parents is every bit as
>precisely defined as the relation: it's the set of
>all people who are related to somebody by the parentOf
>relation. 100% correspondence. No problems there.
>
>AP> Unlike Guarino/Welty I don't think this issue can
> > be made completely strict, but it's certainly
> > advantageous to maintain identity criteria that
> > are as strict as possible.
>
>Talking about something being not completely strict
>is like saying someone is not completely pregnant.
>
>In any case, I'm glad that you agree that their notion
>is not "completely strict". Whenever Nicola gives his
>identity criteria, he uses words like "essence", which
>he never defines. He claims that it is a modal notion,
>which can be represented by a box operator in modal
>logic, but he never explains the basis for those boxes.
>
>As I have pointed out repeatedly, every modal notion
>is definable in terms of some law that serves as the
>basis for the necessity or possibility. And given
>any such law p, all you have to do is to parametrize
>it by means of a lambda expression (or any similar
>mechanism) to get a relation p(x) or p(x,y).
>
>Once you have a relation p(x,y), you go back to
>step #1 and define the set of all x's for which
>there exist some y that satisfies the relation p(x,y).
>
>The set of all parents may change over time, but
>so does the set of all people. In fact, there is
>an interesting relationship between their rates
>of change.
>
>John