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RE: [SKOS]: [ISSUE 44] BroaderNarrowerSemantics

From: Reul, Q. H. <q.reul@abdn.ac.uk>
Date: Thu, 13 Dec 2007 15:49:28 -0000
Message-ID: <2AD2401FC36E784094D0B3375FDA6CE802788F93@VMAIL2.uoa.abdn.ac.uk>
To: "Miles, AJ \(Alistair\)" <A.J.Miles@rl.ac.uk>, <public-swd-wg@w3.org>, <public-esw-thes@w3.org>

Hi Alistair,

I gather that I have started a very interesting question with regard to
this issue. I'm looking at using SKOS to represent thesauri from which I
can extract links between concepts given a semantic relation (i.e.
skos:broader, skos:narrower or skos:related). The advantage of using
SKOS to do this is that it can be re-used by others and people can use
there own thesaurus within their own system.

I realise that the use of API such as Jena, would enable me to traverse
the SKOS graph and therefore extract these links. In his answer, Antoine
[1] speaks about creating local transitive but then you [2] highlighted
potential problems when application use both vocabularies with
"transitive" and "non-transitive" relations. 

For these vocabulary to be fully across multiple applications (as
intended), I believe that semantic relations can't be either
"transitive" or "non-transitive". Otherwise, the working group should
give proper guidelines on how to deal with such occurrences.

Best regards,

Quentin

[1] http://lists.w3.org/Archives/Public/public-swd-wg/2007Nov/0070.html
[2] http://lists.w3.org/Archives/Public/public-swd-wg/2007Dec/0018.html


-----Original Message-----
From: Miles, AJ (Alistair) [mailto:A.J.Miles@rl.ac.uk] 
Sent: 12 December 2007 17:48
To: Reul, Q. H.; public-swd-wg@w3.org; public-esw-thes@w3.org
Subject: RE: [SKOS]: [ISSUE 44] BroaderNarrowerSemantics

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.

However...

> 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!

Cheers,

Al.


> 
> [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
Didcot
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 Thursday, 13 December 2007 15:49:43 GMT

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