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>

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 MenzelReceived on Wednesday, 1 October 2003 13:00:53 UTC

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