From: Antoine Zimmermann <antoine.zimmermann@deri.org>

Date: Fri, 31 Jul 2009 15:32:35 +0100

Message-ID: <4A730083.8070409@deri.org>

To: Christine Golbreich <cgolbrei@gmail.com>

CC: W3C OWL Working Group <public-owl-wg@w3.org>

Date: Fri, 31 Jul 2009 15:32:35 +0100

Message-ID: <4A730083.8070409@deri.org>

To: Christine Golbreich <cgolbrei@gmail.com>

CC: W3C OWL Working Group <public-owl-wg@w3.org>

Christine, What I'm asking for is not a formula. The text is currently saying the same thing in a pretty clear way. I am just asking for a clarification, in case someone *do not* take a close look at the formal definition and wrongly assume that asymmetry is the negation of symmetry. A sentence like: "To say that a property is asymmetric is therefore stronger than saying the property is not symmetric." would be enough. I am raising this point because another person independently understood "asymmetric" in the same way I did, and he was puzzled by the formal definition which did not coincide with his notion of asymmetry. He was understanding this as an error of terminology. In fact, for non-logicians or non-mathematicians, "asymmetric" is usually used as a synonym of "not symmetric". A lot of examples can be found in physics, biology, sociology and even in mathematics (asymmetric matrix, asymmetric geometric figure, etc). Regards, AZ. Christine Golbreich wrote: > Initially there were the mathematical fomula clarifying these > features, as I thought it usefeul for users to prevent any > misunderstanding but I was asked to cut it to shorten the doc > > It's still there in the source code and if wanted I can easily restore it. > > <!-- An asymmetry axiom means --> - that is > if the property expression OPE holds between the individuals <span > class="name">x</span> and <span class="name">y</span>, then it cannot > hold between <span class="name">y</span> and <span > class="name">x</span>. <!--, or in mathematical notation, this is: > > ∀''x'' ∀''y'' (''x'' OPE ''y'') ⇒ ¬ (''y'' OPE ''x'') --> > > cg > > 2009/7/31 Antoine Zimmermann <antoine.zimmermann@deri.org>: >> Dear all, >> >> Until today, I did not look at the semantics of AsymmetricProperty because >> the word was familiar enough to me to intuitively understand it. I was >> however wrongly assuming that the word was used to denote non-symmetric. >> From a linguistic perspective, asymmetry is a lack or absence of symmetry. >> Some mathematical texts use "asymmetric" to simply mean "not symmetric". >> >> I am aware that "asymmetric relation" is often used in mathematics to denote >> "strongly asymmetric relation", i.e., no pairs of elements are related in a >> bidirectional (symmetric) way. While it is perfectly ok that OWL2 defines >> AsymmetricProperties the way it does, I am surprised not to find *any* >> remark, neither in the formal specs, nor in the UFDs, nor in the mailing >> list archives, about the fact that AsymmetricProperty is not the complement >> of SymmetricProperty. >> >> I am sure that other people are understanding asymmetry in the same way as I >> did, so I'd suggest adding a small sentence in the Primer (Sect.6.1 [1]) and >> NF&R (Sect.2.2.3 [2]) stating that "asymmetric" is not the negation of >> "symmetric". Since the UFDs are still in LC, this should be addressed >> somehow. >> >> [1] >> http://www.w3.org/TR/2009/WD-owl2-primer-20090421/#Property_Characteristics >> [2] >> http://www.w3.org/TR/2009/WD-owl2-new-features-20090421/#F6:_Reflexive.2C_Irreflexive.2C_and_Asymmetric_Object_Properties >> >> Regards, >> -- >> Antoine Zimmermann >> Post-doctoral researcher at: >> Digital Enterprise Research Institute >> National University of Ireland, Galway >> IDA Business Park >> Lower Dangan >> Galway, Ireland >> antoine.zimmermann@deri.org >> http://vmgal34.deri.ie/~antzim/ >> >> > > > -- Antoine Zimmermann Post-doctoral researcher at: Digital Enterprise Research Institute National University of Ireland, Galway IDA Business Park Lower Dangan Galway, Ireland antoine.zimmermann@deri.org http://vmgal34.deri.ie/~antzim/Received on Friday, 31 July 2009 14:33:16 UTC

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