From: Jeremy Carroll <jjc@hplb.hpl.hp.com>

Date: Mon, 30 Sep 2002 19:05:35 +0100

To: "Ian Horrocks" <horrocks@cs.man.ac.uk>, "pat hayes" <phayes@ai.uwf.edu>

Cc: <www-webont-wg@w3.org>

Message-ID: <ENEKKODIOPDFKPGAOLNIMEAACAAA.jjc@hpl.hp.com>

Date: Mon, 30 Sep 2002 19:05:35 +0100

To: "Ian Horrocks" <horrocks@cs.man.ac.uk>, "pat hayes" <phayes@ai.uwf.edu>

Cc: <www-webont-wg@w3.org>

Message-ID: <ENEKKODIOPDFKPGAOLNIMEAACAAA.jjc@hpl.hp.com>

Pat: > Range(P, A) -> (forall x,y P(x,y) -> A(y) ) > > You want > > Range(P,A) <-> (forall x,y P(x,y) -> A(y) ) > Ian: > I am agnostic about which of these is to be preferred - as a humble > engineer, all I need to know is which one it is so that I have a clear > spec to which I can build my systems. > One point that is worth making though is that there are a number of > similar statements that can be made about OWL properties, and that it > may make sense to give them a uniform semantics, i.e., all treated as > implication or all treated as bi-implication. E.g., we also have: > Domain(P,C) implies/iff (forall x,y P(x,y) -> C(x)) > TransitiveProperty(P) implies/iff (forall x,y,z (P(x,y) ^ P(y,z)) -> P(x,z)) > SymmetricProperty(P) implies/iff (forall x,y P(x,y) -> P(y,x)) > FunctionalProperty(P) implies/iff (forall x,y,z (P(x,y) ^ P(x,z)) -> y=z) > InverseFunctionalProperty(P) implies/iff (forall x,y,z (P(y,x) ^ P(z,x)) -> y=z) > inverseOf(P,Q) implies/iff (forall x,y P(x,y) -> Q(y,x)) > We already had the discussion w.r.t. transitive (or was it > functional). I argued for implies semantics, but the general view > seemed to be that iff semantics should hold (and by extension that it > should hold for all the above statements). My recollection was that: - no decision was made - Jos and me rather agreed with the sentiments you express here. vis + Either can be made to work; + they probably should all be iff or all be implies; + a decision is needed agnostically yours JeremyReceived on Monday, 30 September 2002 14:02:27 GMT

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