From: Pascal Hitzler <hitzler@aifb.uni-karlsruhe.de>

Date: Tue, 04 Aug 2009 14:15:48 +0200

Message-ID: <4A782674.5000301@aifb.uni-karlsruhe.de>

To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>

CC: Antoine Zimmermann <antoine.zimmermann@deri.org>, Michael Schneider <schneid@fzi.de>, W3C OWL Working Group <public-owl-wg@w3.org>

Date: Tue, 04 Aug 2009 14:15:48 +0200

Message-ID: <4A782674.5000301@aifb.uni-karlsruhe.de>

To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>

CC: Antoine Zimmermann <antoine.zimmermann@deri.org>, Michael Schneider <schneid@fzi.de>, W3C OWL Working Group <public-owl-wg@w3.org>

Yes and I've added this to the primer. http://www.w3.org/2007/OWL/wiki/index.php?title=Primer&diff=25059&oldid=25056 Pascal. Ian Horrocks wrote: > I think that we are in vehement agreement here. A very small addition to > Primer and NF&R pointing out that asymmetric is much stronger than > simply not symmetric (and vice versa) seems harmless and might even > eliminate a source of possible confusion. > > Ian > > > > On 31 Jul 2009, at 19:35, Antoine Zimmermann wrote: > >> Michael, >> >> You are right, there is probably no interesting use case for the >> non-symmetric properties. I just didn't think about it when I was >> assuming non-symmetry. >> >> I admit that "asymmetric relations" in logics is (apparently) >> exclusively defined as in OWL 2 (which is indeed the only definition >> that is really useful). >> >> However, it is the case that "asymmetric", even in mathematics, is >> used as a place-holder for "not symmetric". You may, though, have to >> consider things out of the restricted case of set-theoretic relations >> (e.g., symmetric numbers, symmetric figures, etc.) For >> non-mathematicians, my experience is that people use >> "asymmetry/asymmetric" in common language for denoting >> non-symmetry/not symmetric (regardless of the domain it is applied to). >> >> My suggestion is simply to evacuate a potential false assumption by >> concisely stating that [asymmetry != non-symmetry]. IMO, it would be >> enough to update Primer and NF&R only, because people who look at the >> formal specs are probably more maths/logic-minded and would not be >> surprised by the definition. >> >> Regards, >> AZ. >> >> Michael Schneider wrote: >>> Hi Antoine! >>> First, let me say that in logics/mathematics literature I have never >>> seen >>> any other use of "asymmetric" than the way we are using it in our >>> documents >>> (the "hard" form). More, I would not easily see any use case for >>> having non-symmetry as a >>> modeling feature. It would tell me something like that for any model >>> of the >>> ontology there would exist some property assertion for which there is no >>> corresponding reverse property assertion; but not knowing which property >>> assertion is meant, and it can be a different one for different >>> models. What >>> does this information buy me? >>> (But if you really like to have non-symmetry as a feature, you can still >>> have it under the RDF-based semantics by stating something like >>> ex:p rdf:type [ owl:complementOf( owl:SymmetricProperty ) ] . >>> This is, of course, not possible in OWL 2 DL. >>> ) >>> But I agree that adding some informative note should be ok, and can >>> even put >>> it in the CRs, IMO. >>> For the RDF-Based Semantics, I think what is already in for some months >>> should be sufficient: >>> [[ >>> If two individuals are related by a symmetric property, then this >>> property >>> also relates them reversely, while this is never the case for an >>> asymmetric >>> property. ]] >>> Agreed? >>> Cheers, >>> Michael >>>> -----Original Message----- >>>> From: public-owl-wg-request@w3.org >>>> [mailto:public-owl-wg-request@w3.org] >>>> On Behalf Of Antoine Zimmermann >>>> Sent: Friday, July 31, 2009 1:21 PM >>>> To: 'W3C OWL Working Group' >>>> Subject: asymmetric VS non-symmetric >>>> >>>> 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_Properti >>>> >>>> es >>>> >>>> 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/ >>> -- >>> Dipl.-Inform. Michael Schneider >>> Research Scientist, Dept. Information Process Engineering (IPE) >>> Tel : +49-721-9654-726 >>> Fax : +49-721-9654-727 >>> Email: michael.schneider@fzi.de >>> WWW : http://www.fzi.de/michael.schneider >>> ======================================================================= >>> FZI Forschungszentrum Informatik an der Universität Karlsruhe >>> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe >>> Tel.: +49-721-9654-0, Fax: +49-721-9654-959 >>> Stiftung des bürgerlichen Rechts, Az 14-0563.1, RP Karlsruhe >>> Vorstand: Prof. Dr.-Ing. Rüdiger Dillmann, Dipl. Wi.-Ing. Michael Flor, >>> Prof. Dr. Dr. h.c. Wolffried Stucky, Prof. Dr. Rudi Studer >>> Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus >>> ======================================================================= >> >> >> -- >> 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/ >> > > > -- PD Dr. Pascal Hitzler pascal@pascal-hitzler.de http://www.pascal-hitzler.de Semantic Web Textbook: http://www.semantic-web-book.orgReceived on Tuesday, 4 August 2009 12:13:06 GMT

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