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Re: [SKOS] Re: SKOS Concept schemes and OWL Ontologies (related to ISSUE-36)

From: Simon Jupp <simon.jupp@manchester.ac.uk>
Date: Thu, 17 Apr 2008 15:04:31 +0100
Cc: <sjupp@cs.man.ac.uk>, <public-esw-thes@w3.org>, <public-swd-wg@w3.org>
Message-Id: <5DB9EA83-0017-4455-86B6-A77C0CBDAD5E@manchester.ac.uk>
To: "Antoine Isaac" <Antoine.Isaac@KB.nl>
Thanks for the response Antoine. I can see what you are saying and see  
the difference between the types of importing you might want to do,  
however, I am not convinced using the owl:imports property is such a  
good idea.  This property already has its intended semantics which  
SKOS is ignoring and I can imagine tools having problems handling this  
statement when parsing RDF (I have already tested it with some editors  
and RDF parsers). owl:imports has a specific function, the typical  
behavior for a tool when it finds owl:imports is to go and find an  
ontology and import it. If the thing at the end of the imports is just  
an instance of skos:ConceptScheme the tools inevitably just fall over  
or ignore it completely.


On 7 Mar 2008, at 09:18, Antoine Isaac wrote:

> Hi Simon,
> It's a good thing that you sent this mail, because it's about a  
> pattern that has been not commented upon a lot outside of the WG.
> In this respect the comment you make is quite true:
> - we have nothing to import concept schemes on an individual basis
> - and (my making it explicit) we have nothing to make the concepts  
> in the imported concept schemes members of the importing concept  
> scheme on a group basis.
> The current solution is purely about containment of datasets  
> (nformation sources? I admit that I'm not a real expert in this part  
> of the RDF world): one information source imports another one, but  
> this does not create extra knowledge that really glues the elements  
> described in these two sources.
> One first way to obtain a better result in your example is to put  
> the 2 concept schemes in different ontologies. The pattern in [1]  
> would indeed expect users that want to exploit owl:import not to  
> mess the concept schemes together.
> Note indeed that this is actually more-or-less required by OWL  
> management of ontology containment, as far as I understand it from  
> [3]. In OWL there is no RDF link between the description of the  
> owl:Ontology instance and the classes and properties that are  
> assumed to belong to it. Everything relies on the containment at the  
> information-source level. I say that my file describes an ontology,  
> and my file happens to contain some class and property descriptions.  
> Remember that actually ontologies do not contain classes and  
> properties, they contain statements/axioms about these.
> So now, why not make concept schemes also always instances of  
> owl:Ontology? Well I guess for advanced users aware of the problems  
> I've just refered to, that could make sense. After all, we really  
> want to say that a concept scheme includes a number of concepts (by  
> means of inScheme) and contains some statements about them (by means  
> of OWL ontology-based containment)
> But I guess many other people just don't care about these  
> subtleties, and would still like to put several concept schemes in a  
> same dataset.
> Considering this, it could make sense to include a skos:imports, as  
> you suggest. This would be a combination of owl:imports and  
> "creation" of skos:inScheme statements between the concepts from the  
> imported CS and the importing one.
> But in the end I think that could be counter-productive, precisely  
> because of the mixture between OWL containment and SKOS membership  
> aspects. I'm afraid users would just interpret it in a natural SKOS  
> way without being really aware of the OWL machinery that is behind  
> and requires extra care with the datasets handled.
> Or we would have to define our own SKOS containment mechanism, very  
> similar to the OWL one by the names that are used, but quite  
> different with respect to what the methods indeed do. Again I'm  
> afraid it would not be really productive, with respect to the  
> compatibility between SKOS and other Semantic Web stuff.
> I was not really enthusiastic about it at the beginning, but now I  
> tend to adhere to the existing solution. It has at least the  
> positive aspect of not fooling the users into thinking it's easy to  
> import concept schemes :-(
> Best,
> Antoine
> [1] http://www.w3.org/TR/skos-primer/#secextension
> [2] http://www.w3.org/TR/skos-reference/#L1170
> [3] http://www.w3.org/TR/owl-ref/#Header
> > De: public-esw-thes-request@w3.org de la part de sjupp@cs.man.ac.uk
> > Date: mer. 05/03/2008 16:36
> > : public-esw-thes@w3.org
> > Objet : SKOS Concept schemes and OWL Ontologies
> >
> >
> > Hi all,
> >
> > I am after some clarity on using owl:imports with respect to concept
> > schemes, hopefully my problem is clear from the examples. I should  
> point
> > out that I create my SKOS vocabularies as OWL ontologies using  
> Protege.
> >
> > So consider an OWL ontology called ONT1, it contains the following
> > instances.
> >
> > ex1:csA rdf:type skos:ConceptScheme
> >
> > ex1:csB rdf:type skos:ConceptScheme
> >
> > I also have an Ontology called ONT2 that conatins:
> >
> > ex2:csC rdf:type skos:ConceptScheme
> >
> > ex2:csC owl:imports ex1:csA
> >
> > What should I expect to get imported into ONT2. I get two different
> > results depending on how I interpret skos:ConceptSchema (i.e as a
> > owl:Class or an owl:Ontology - If I am correct it is consistent in
> > SKOS to do both)
> >
> > 1) ONT2 imports only the concepts that are in concept scheme csA?
> > (which is what I want to happen)
> >
> > 2) ONT2 imports all of ONT1? (which is how it could be interpreted
> > because of the semantics of owl:imports)
> >
> > If owl:imports is to be used with concept schemes then why not  
> always
> > treat concept schemes to be the same as owl:Ontologies?  Was the
> > possibility of a skos:imports ever discussed by the working group?
> >
> > Cheers,
> > Simon
> >
> > Simon Jupp
> > simon.j...@manchester.ac.uk
> > http://www.cs.man.ac.uk/~sjupp/
> >
> >
> >

Simon Jupp
Received on Thursday, 17 April 2008 15:14:05 UTC

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