Re: Some questions about the exact meanings

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 01 Oct 2003 13:09:29 -0400 (EDT)
Message-Id: <20031001.130929.09560176.pfps@research.bell-labs.com>

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From: Chris Menzel <cmenzel@tamu.edu>
Subject: Re: Some questions about the exact meanings
Date: Wed, 1 Oct 2003 11:51:03 -0500

>
> 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.

I thought that his question was which stance OWL took.

> 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

Well, yes, but this is an entirely different question.

peter
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Received on Wednesday, 1 October 2003 13:09:57 UTC

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