RE: OWL2 comments -> UC#3

Ian Horrocks wrote:

>It may not be super useful/used in actual applications, but I don't
>see what is wrong with our old friend the Narcissist for illustrating/
>motivating local reflexivity. Clearly every instance of this class
>loves his/her-self, but it is clearly not true to say that loves is
>reflexive in general.
>
>Ian

FWIW, the Narcissist isn't particularly loved by myself. :-)

I consider global and local reflexivity and irreflexivity useful for modeling notions of inclusion.
 
An obvious example would be the skos:broader relation on the class skos:Concept. It is certainly not nonsensical to say that every concept is broader than itself, i.e. that concepts include themselves. Likewise, it might make sense in certain situations to state that no concept is broader than itself at all. 

The current working draft of the SKOS reference neither defines reflexivity nor irreflexivity for skos:broader [1]. With reflexivity and irreflexivity, OWL 2 allows people to add one of these two additional constraints on demand. And self restrictions are even more fine grained, by allowing to state that skos:broader should only be locally reflexive w.r.t. skos:Concept. Or, alternatively, one can make skos:broader locally irreflexive w.r.t. skos:Concept via

  SubClassOf( 
      skos:Concept 
      ComplementOf(HasSelf(skos:broader)) 
  )

i.e. if x in skos:Concept, then NOT( x skos:broader x ).

Best,
Michael

[1] <http://www.w3.org/TR/skos-reference/#L2449>

--
Dipl.-Inform. Michael Schneider
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