Re: asymmetric VS non-symmetric

Hi all,

I brought this up because I had heard of "antisymmetric" but not of "asymmetric"
and didn't know the difference. 

To me a primer should explain the concept broadly, in relation to concepts I
already know, and point to where more explanation can be found. I would propose
something that is actually shorter than the current text: 


"Note that asymmetry is a stronger notion than anti-symmetry as it requires that
the relationship is also irreflexive."

instead of

"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."


(I think the 2nd sentence is not needed here as the subject is asymmetry; this
is more appropriate for the paragraph about symmetry. It also is more complex
and thus less helpful to explain asymmetry.)


Create links for the terms "asymmetry", "anti-symmetry" and "irreflexivity"
(e.g. wikipedia) and it's what I would need from a "primer".

Regards,
Mark van Assem.

> Hi Rinke,
> 
> yes, one could add more explanation regarding asymmetric properties  
> --- but I doubt whether the primer is the right place: it's a *prime*r  
> (as in 'first starting point'), and thus won't be the place to provide  
> exhaustive clarifications of all subtleties and explanations of all  
> possible misunderstandings. I can think of/remember many questions/ 
> misunderstandings of OWL constructors, and also how they interact, and  
> I don't want to see  asymmetric properties being singled out as the  
> one feature that is explained in depth...
> 
> Cheers, Uli
> 
> On 2 Sep 2009, at 15:56, Rinke Hoekstra wrote:
> 
> > 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 Thursday, 3 September 2009 12:34:40 UTC