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Re: asymmetric VS non-symmetric

From: Rinke Hoekstra <hoekstra@few.vu.nl>
Date: Wed, 2 Sep 2009 16:56:53 +0200
Cc: Mark van Assem <mark@cs.vu.nl>
Message-Id: <1E3AA575-7095-41D7-9CF0-BC0D918441A5@few.vu.nl>
To: OWL 2 <public-owl-wg@w3.org>
Hi all,

I just had a request from Mark van Assem to add an extra explanation  
to the primer about asymmetry.

Pascal's addition to the primer [1] is fine:

"Note that being asymmetric is a much stronger notion than being non- 
symmetric. Likewise, being symmetric is a much stronger notion than  
being non-asymmetric. "

... but a bit short and could introduce additional confusion (what  
then does non-symmetry mean? and non-asymmetric?). Also, it might be  
helpful to say something along the lines that asymmetry is anti- 
symmetry + irreflexivity (anti-symmetry and asymmetry are easily  
confused).

The primer would be the right place for this addition.

-Rinke

[1] http://www.w3.org/2007/OWL/wiki/index.php?title=Primer&diff=25059&oldid=25056


On 5 aug 2009, at 09:40, Christine Golbreich wrote:

> 2009/8/4 Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>:
>> Can we have a diff please.
>>
>> Thanks,
>> Ian
>
>
> - for profiles
> http://www.w3.org/2007/OWL/wiki/index.php?title=New_Features_and_Rationale&diff=prev&oldid=25076
> - for asymmetric
> http://www.w3.org/2007/OWL/wiki/index.php?title=New_Features_and_Rationale&diff=prev&oldid=25052
>
> cg
>
>
>> On 4 Aug 2009, at 18:58, Christine Golbreich wrote:
>>
>>> Note on asymmetric properties and profiles added in NF&R
>>>
>>> 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/
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Christine
>>>
>>
>>
>
>
>
> -- 
> Christine





---
Drs Rinke Hoekstra

Leibniz Center for Law      |  AI Department
Faculty of Law              |  Faculty of Sciences
Universiteit van Amsterdam  |  Vrije Universiteit
Kloveniersburgwal 48        |  De Boelelaan 1081a
1012 CX  Amsterdam          |  1081 HV Amsterdam
+31-(0)20-5253499           |  +31-(0)20-5987752
hoekstra@uva.nl             |  hoekstra@few.vu.nl

Homepage: http://www.few.vu.nl/~hoekstra
Received on Wednesday, 2 September 2009 14:57:30 GMT

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