W3C home > Mailing lists > Public > public-owl-wg@w3.org > August 2009

Re: asymmetric VS non-symmetric

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Mon, 3 Aug 2009 16:52:10 +0200
Cc: Antoine Zimmermann <antoine.zimmermann@deri.org>, Michael Schneider <schneid@fzi.de>, W3C OWL Working Group <public-owl-wg@w3.org>
Message-Id: <8A34087A-56AE-4EF0-8BDD-0B1F55F245FB@uva.nl>
To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
On 3 aug 2009, at 16:40, 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.

+1

-Rinke

>
> 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/
>>
>



---
Drs Rinke Hoekstra

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Received on Monday, 3 August 2009 14:52:51 GMT

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