# Re: asymmetric VS non-symmetric

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>
```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:

&forall;''x'' &forall;''y'' (''x'' OPE ''y'') &rArr; &not; (''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
> Lower Dangan
> Galway, Ireland
> antoine.zimmermann@deri.org
> http://vmgal34.deri.ie/~antzim/
>
>

--
Christine
```
Received on Friday, 31 July 2009 13:12:57 UTC

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