RE: RE : Suggestion for SKOS FAQ

I agree with Andy, I also think it should be a sub-property, not a
super-property...
 
Regards
Margherita

	-----Original Message-----
	From: public-esw-thes-request@w3.org
[mailto:public-esw-thes-request@w3.org] On Behalf Of Andreas Langegger
	Sent: 11 March 2008 12:14
	To: Alasdair J G Gray
	Cc: Antoine Isaac; Simon Spero; iperez@babel.ls.fi.upm.es; SKOS
	Subject: Re: RE : Suggestion for SKOS FAQ
	
	
	Hi, 

	first I din't pay much attention to your discussion, because I
thought this case is clear... looking at the spec I read
"skos:broaderTransitive owl:subClassOf skos:broader" - but there it says (to
my surprise): skos:broaderTransitive and others are "super properties" - why
that?

	If I would model this I would say:

	skos:semanticRelation a owl:ObjectProperty .
	skos:broader a skos:semanticRelation .
	skos:narrower a skos:semanticRelation .
	skos:broaderTransitive a skos:broader; a owl:TransitiveProperty .
	skos:narrowerTrasnsitive a skos:narrower; a owl:TransitiveProperty .
	and so on...

	can anybody comment on this why the specs says "super property" and
not "sub property" ?
	Whith the statements above I can deceide whether to allow
transitivity or not. And because of OWA, skos:broader not explicitly asserted
as a transtive property, it does not mean, that it _cannot be_ transitive,
sure it can, but it does not need to be valid.

	If a taxonomy should be ISO2788 compliant, just use the *Transitive
versions - so it's up to the modeler and not to the application which I think
is fine.
	
	
	regards
	Andy


	On Mar 11, 2008, at 10:46 AM, Alasdair J G Gray wrote:


		Hi Antoine,
		
		I've got to admit that in reading the SKOS Primer [2], in
particular sections 2.3.1 and 4.7, I became very confused as to the
properties of skos:broader and skos:broaderTransitive. In particular the fact
that skos:broaderTransitive is a super property of skos:broader.
		
		However, reading your mail below has cleared things up for
me. Perhaps the primer should be more explicit in the difference.
		
		Cheers,
		
		Alasdair
		
		[2] http://www.w3.org/TR/skos-primer/

		
		Antoine Isaac wrote: 


			Hi Simon,
			
			Two objections to your mail:
			
			1. I still don't get it why ISO2788 says BT *should*
be transitive. Of course there can be interpretations that leads to this, but
it's still not 100% clear to me. Can you quote a sentence that makes you say
so?
			
			2. In the exemple you give, SKOS does not prohibit A
broader C. We say that broader is *not transitive*, that different from
saying that it is *intransitive* (or "antitrantisitive") ! "transitivity does
not hold" does *not* mean that (NOT A broader C) is valid in all cases.
			
			Maybe actually point 2 is an answer to point 1, if
you got our proposal for skos:broader semantics wrong.
			To sum up:
			- from A skos:broader B, B skos:broader C you cannot
automatically infer A skos:broader C: there are concept schemes for which
this would be assuming too much coherence for the hierarchical links.
			- there can be concept schemes for which the
co-existence A skos:broader B, B skos:broader C and A skos:broader C is OK.
Maybe all thesauri that are compliant with ISO2788, if ISO2788 say BT is
always transitive. But the A skos:broader C was in that case produced by some
knowledge that is not in the SKOS semantics.
			
			Does it make the situation clearer? You can also go
to [1], when Alistair noticed this subtle differences (that had been also
interfering with the SWD working group discussions)
			
			Best,
			
			Antoine
			
			[1]
http://lists.w3.org/Archives/Public/public-esw-thes/2007Dec/0052.html

			
			-------- Message d'origine--------
			De: public-esw-thes-request@w3.org de la part de
Simon Spero
			Date: ven. 07/03/2008 23:58
			À: al@jku.at
			Cc: iperez@babel.ls.fi.upm.es; SKOS
			Objet : Re: Suggestion for SKOS FAQ
			
			On Fri, Mar 7, 2008 at 4:54 PM, Andreas Langegger
<al@jku.at> <mailto:al@jku.at>  wrote:
			
			>
			>  thanks for the pointer to issue-44. I didn't read
deep into the thread.
			> But as Antoine pointed out, there is the transitive
version also (obviously
			> the result of the issue-44 discussion). So both
kinds of semantics can be
			> expressed in the model and are not defined by the
application.
			>
			
			The problem with the introduction of an intransitive
"broader" relationship
			is that such a relationship is fundamentally
incompatible with the Broader
			Term relationship as defined in ISO-2788 et. al.
			
			The defining characteristic of hierarchical
relationships  is that they are
			totally inclusive.  This property absolutely requires
transitivity.  If this
			condition does not apply, the relationship is
associative, not hierarchical.
			  Renaming the broader and narrower term
relationships doesn't change this;
			all it has done is cause confusion.
			
			As an example of the confusion so caused, note that
associative
			relationships remain disjoint from broaderTransitive
(S24)?    If "broader"
			can be intransitive, this constraint is inexplicable.
			
			Let A,B,C be Concepts,
			       A broader B,
			       B broader C,
			
			and suppose that transitivity does not hold (  NOT A
broader C)
			
			By S18,  we have
			      A broaderTransitive B,
			      B broaderTransitive C,
			By S21,
			      A broaderTransitive C
			
			and hence, by S24,
			      NOT A related B,
			      NOT B related C,
			      NOT A related C
			
			We have NOT A broader C and NOT A related C, so there
can't be any
			relationship between A and C  at all!
			
			Simon
			
			


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		Dr Alasdair J G Gray
		http://www.dcs.gla.ac.uk/~agray/

		
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