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Re: Some questions about the exact meanings

From: Chris Menzel <cmenzel@tamu.edu>
Date: Wed, 1 Oct 2003 11:51:03 -0500
To: www-rdf-logic@w3.org
Message-ID: <20031001165103.GQ27429@tamu.edu>

On Wed, Oct 01, 2003 at 09:36:32AM -0400, Peter F. Patel-Schneider wrote:
> 
> From: Tanel Tammet <tammet@staff.ttu.ee>
> > ...
> > First, suppose we want to say that "P" is a symmetric property.
> > 
> > We can axiomatize what "symmetric" means by:
> > 
> > forall X,Y,Z.  holds(symmetric,X,Y) <=>
> >                          (holds(X,Y,Z) => holds(X,Z,Y)).
> 
> I think that you meant to say
> 
>   forall X,Y,Z.  holds(symmetric,X) <=>
>                            (holds(X,Y,Z) => holds(X,Z,Y)).
> > The question is whether in OWL the equivalence <=>
> > in this definition should really be an implication =>
> > or it should be an equivalence <=>
> > 
> > What is the _right_ axiom schema for OWL: with implication
> > or with equivalence?
> 
> ...the answer is <=>.  OWL generally takes an extensional stance on
> such questions.  If the conditions for some characteristic hold, then
> the characteristic holds.

I think that's just Tanel's question, though.  Do you really want
"Loves", say, to be classified as a symmetric relation if it just
happens to turn out in one's domain that all love is requited?

Chris Menzel
Received on Wednesday, 1 October 2003 13:00:53 GMT

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