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RE: [SKOS]: [ISSUE 44] BroaderNarrowerSemantics

From: Miles, AJ \(Alistair\) <A.J.Miles@rl.ac.uk>
Date: Wed, 12 Dec 2007 17:48:28 -0000
Message-ID: <677CE4DD24B12C4B9FA138534E29FB1D03B3FAB4@exchange11.fed.cclrc.ac.uk>
To: "Reul, Q. H." <q.reul@abdn.ac.uk>, <public-swd-wg@w3.org>, <public-esw-thes@w3.org>

Hi Quentin,

> I think [ISSUE 44] might have been resolved at the f2f in 
> Amsterdam a few months ago as I think to remember that we 
> would allow people to use skos:broader/skos:narrower as both 
> transitive and intransitive.
> However, I believe that these semantic relations should be 
> made transitive. For each skos:ConceptScheme, there might 
> have one or more top concept and there might have several 
> subconcepts available for each of them. 
> Example:
> skos:ConceptScheme W
> W skos:hasTopConcept X
> X skos:narrower Y
> Y skos:narrower Z
> The user might want to know that Z skos:broader X. Or would 
> simple graph operation be enough to find all the sub- or 
> super- concepts?

Out of interest, what is the use case you are thinking of? Why does your user need to know Z skos:broader X?

Given a concept, if you want to find all concepts above ("parents") and below ("children") in the broader/narrower hierarchy, you could do this programmatically, using an API like Jena, in which case you don't need to do any transitive reasoning. 

However, if you want to use a query language like SPARQL, and you want to find e.g. all "parent" concepts in a single query, then you would have to do some transitive reasoning first, and query the graph that includes your inferred triples.

Note that I think there are two separate questions here. 

One question is, how do I implement a specific piece of functionality in software, e.g. find all parents or children of a given concept in a broader/narrower hierarchy. One possible solution to this question is to use transitive reasoning. However, to achieve this you *don't* need skos:broader rdf:type owl:TransitiveProperty to be a *standard part of SKOS* -- you can do whatever you like within the confines of your application. 

It is a completely separate question to ask, if I am sharing some SKOS data, can I share the axiom skos:broader rdf:type owl:TransitiveProperty with others? Can I share data inferred using this axiom with others? The answers to these questions *do* depend on what we put in the SKOS standard.

> Furthermore, we have defined a skos:Concept rdf:type 
> owl:Class and hence skos:broader and skos:narrower could be 
> used to describe owl:Class in ontologies. 

This does not follow. 

It would follow we stated 

skos:Concept rdfs:subClassOf owl:Class.

but that is a very different statement from 

skos:Concept rdf:type owl:Class.


> I'm not sure that 
> we want skos:semanticRelation to be applied between owl:Class.

... our semantics for SKOS do not prohibit using skos:semanticRelation, skos:broader, skos:narrower or skos:related between two classes!



> [ISSUE 44] http://www.w3.org/2006/07/SWD/track/issues/44
> ******************************************
> * Quentin H. Reul                        *
> * PhD Research Student                   *
> * Department of Computing Science        *
> * University of Aberdeen, King's College *
> * Room 238 in the Meston Building        *
> * ABERDEEN AB24 3UE                      *
> * Phone: +44 (0)1224 27 4485             *
> * http://www.csd.abdn.ac.uk/~qreul       *
> ******************************************

Alistair Miles
Research Associate
Science and Technology Facilities Council
Rutherford Appleton Laboratory
Harwell Science and Innovation Campus
Oxfordshire OX11 0QX
United Kingdom
Web: http://purl.org/net/aliman
Email: a.j.miles@rl.ac.uk
Tel: +44 (0)1235 445440  
Received on Wednesday, 12 December 2007 17:57:22 UTC

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