From: Christine Golbreich <cgolbrei@gmail.com>

Date: Fri, 31 Jul 2009 15:12:16 +0200

Message-ID: <b0ed1d660907310612r35f55522l2191071bc148fddc@mail.gmail.com>

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

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

Date: Fri, 31 Jul 2009 15:12:16 +0200

Message-ID: <b0ed1d660907310612r35f55522l2191071bc148fddc@mail.gmail.com>

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

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

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/ > > -- ChristineReceived on Friday, 31 July 2009 13:12:57 UTC

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