Concept Equivalence, IFPs, skos:subjectIndicator and owl:sameAs (was Re: SKOS Guide and owl:sameAs)

Hello,

Firstly I am new to SKOS, so apologies if this has come up before.

The SKOS guide (as indicated in this thread) discourages the use of owl:sameAs to establish equivalence relations between skos:Concepts because:

<http://www.w3.org/TR/swbp-skos-core-guide/#secidentity>
"The property owl:sameAs should not be used to express the fact that two conceptual 
resources (i.e. resources of type skos:Concept) share the same meaning. The property 
owl:sameAs implies that two resources are identical in every way (they are in fact 
the same resource). Although two conceptual resources may have the same meaning, 
they may have different owners, different labels, different documentation, different 
history, and of course a different future."

However, the use of skos:subjectIndicator, defined inverse functional, is described in:

<http://www.w3.org/TR/swbp-skos-core-guide/#secpsi>
"The property skos:subjectIndicator allows you to assert a link between a concept 
and a human-readable document that provides a complete, definitive description of that concept.
...
The skos:subjectIndicator property is an owl:InverseFunctionalProperty, which means that 
if any two nodes in an RDF graph have the same value for this property, then they are the 
same resource [OWL]. Therefore you can use the skos:subjectIndicator property to 
indirectly identify a concept by reference to the URI of the document that is the 
published subject indicator for that concept."

So... if the same skos:subjectIndicator is asserted for two (or more) skos:Concepts then it can be inferred that they are the same skos:Concept which seems to be at odds with the desire *not* to establish such equivalences as expressed in the narrative above discouraging the use of owl:sameAs.

Is there a reason why concept equivalences established via the skos:subjectIndicator are "good" and equivalencies established via owl:sameAs are bad?

Thanks,

Stuart Williams
--
HP Labs, Bristol.

> Hi,
>
> There is a confusion of different things here.
> 
> 1- skos:Concept is a class.
> 2- instances of skos:Concept are called "concepts" in the SKOS documents.
> 
> 3- mapping of skos:Concept to another class can be done with 
> owl:equivalentClass
> 4- mapping of instances of skos:Concept to other skos:Concept 
> instances (from other vocabularies) can be done with owl:sameAs
> 5- mapping of instances of skos:Concept to other instances (from other 
> vocabularies) can also be done with the SKOS mapping properties, e.g. 
> exactMatch [1]
> 
> Now the confusion is about which kind of mapping (3-5) is meant. The 
> "Concept Identity and Mapping" section [2] states that mapping type 4 
> should not be used, instead type 5 is better. This is because the 
> former states that they are the same *in every respect*, while the 
> latter only states that their extensions are the same (set of docs 
> indexed with one concept is also properly indexed with the other). If 
> you use the former you also merge their metadata, e.g. date of 
> creation and scheme they belong to. They become indistinguishable. The 
> latter keeps them distinguishable.
> 
> The text mentioned does not refer to type 3 at all. This mapping would 
> be required if someone is not using the SKOS schema for a vocabulary, 
> but  something similar. Then a mapping
>
>	skos:Concept owl:equivalentClass my:Concept
>
> can be used to make all instances of my:Concept also skos:Concepts, so 
> they can be manipulated by software that understands SKOS.
> 
> Hope this helps,
> Mark.
> 
> [1]http://www.w3.org/2004/02/skos/mapping/spec/#exactMatch
> [2]http://www.w3.org/TR/2005/WD-swbp-skos-core-guide-20051102/#secidentity
> 
> Nabonita Guha wrote:
> > */Bernard Vatant <bernard.vatant@mondeca.com>/* wrote:
> > 
> >  >A skos:Concept is not a class, and the domain of owl:equivalentClass is
> >  >owl:Class
> > 
> > Whereas in SKOS Core guide 
> > (http://www.w3.org/TR/2005/WD-swbp-skos-core-guide-20051102/#secconcept), 
> > skos:Concept has been described as a class. If it's not a Class then 
> > what it can be considered as?
> > 
> > Best,
> > 
> > Nabonita Guha
> > 
> > Senior Research Fellow
> > Documentation Research & Training Centre
> > Indian Statistical Institute
> > Bangalore INDIA
> > 
> > 
> > 
> > 
> > 
> >     Hi Andrew
> >      > The SKOS guide [1], in the "Concept Identity and Mapping"
> >     section, states that owl:sameAs *should not* be used to indicate
> >     that two concepts share the same meaning. It gives some rationale in
> >     the section for this. Looking at the OWL guide [2], in the "4.1.
> >     Equivalence between Classes and Properties" section, I'm wondering
> >     whether one can use owl:equivalentClass to indicate that two
> >     concepts share the same meaning. If there is a reason why
> >     owl:equivalentClass can/cannot be used for this, should it also be
> >     mentioned in "Concept Identity and Mapping" section?
> >      >
> >     Yes, there is a good reason.
> >     A skos:Concept is not a class, and the domain of owl:equivalentClass is
> >     owl:Class
> > 
> >     Cheers
> > 
> >     Bernard
> > 
> >      >
> >      > Thanks, Andy.
> >      >
> >      > [1]
> >      > [2]
> >      >
> >      >
> >      >
> > 
> >     -- 
> > 
> >     *Bernard Vatant
> >     *Knowledge Engineering
> >     ----------------------------------------------------
> >     *Mondeca**
> >     *3, cité Nollez 75018 Paris France
> >     Web: www.mondeca.com
> >     ----------------------------------------------------
> >     Tel: +33 (0) 871 488 459
> >     Mail: bernard.vatant@mondeca.com
> >     Blog: Leçons de Choses
> > 
> > 
> > 
> > ------------------------------------------------------------------------
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> 
> -- 
>   Mark F.J. van Assem - Vrije Universiteit Amsterdam
>         markREMOVE@cs.vu.nl - http://www.cs.vu.nl/~mark

Received on Thursday, 2 November 2006 16:31:07 UTC