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Re: Concept Coordination text for SKOS Primer

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Tue, 19 Aug 2008 12:30:59 +0200
Message-ID: <48AAA0E3.9020006@few.vu.nl>
To: Ed Summers <ehs@pobox.com>
CC: SWD WG <public-swd-wg@w3.org>

Hi Ed,

Thanks a lot! It's generally well-written, I believe we can put it in 
the Primer. And I'll do it right now.
Some comments however, explaining what will appear online in a couple of 
> It's been a busy summer, and a long time coming, but here it is. If
> you have the energy please give it a read over to make sure that 1) I
> characterize the difference between pre and post-coordination
> correctly; 

I think it is wholy ok. I'm however not comfortable with what I'd call 
"implicit" pre-coordination:
> for example, if a
> concept scheme includes a concept for "Bicycle Repair" it is
> considered to be pre-coordinated concept of the concept "Bicycle" and
> "Repair". 

I'm not sure this is always pre-coordination, actually. I mean, I can 
see why it could be, but I feel that in some cases "bicycle repair" 
might have been introduced in a KOS without any questioning about other 
concepts pre-existing or not.
To avoid misunderstandings and long debates (which are likely to occur 
if we say things like that) I prefer to go straight to more "explicit" 
pre-coordination cases, in which the original concepts are recognizable 
by syntactic means, like "Bicycles--Repairing". I hope you don't mind...

> 2) the alternatives including ex:coordinationOf,
> owl:unionOf and SPARQL are sound ;

Apart from what I think is a Turtle error (the use of comma in the list 
representation) I think those examples and patterns perfectly are sound!

>  and that 3) I captured the spirit
> of this decision appropriately.

I believe this is perfect. I hope other SWD members won't object. Abyway 
comments on today's Primer will be more than welcome ;-)

> 4.4 Coordinating Concepts
> Indexing practices involving thesauri and other KOS often include the
> notion of coordination. Coordination is an activity in which concepts
> from a KOS are combined together. In general there are two kinds of
> coordination: pre-coordination [1] and post-coordination [2]. The key
> distinction between the two hinges on when the actual coordination
> occurs in relation to an information retrieval event.
> Pre-coordination is done prior to information retrieval, by a KOS
> maintainer, or by an indexer who is using a KOS. For example, if a
> concept scheme includes a concept for "Bicycle Repair" it is
> considered to be pre-coordinated concept of the concept "Bicycle" and
> "Repair".  In addition it is also considered to be pre-coordination
> when an indexer takes two existing concepts from a concept scheme,
> like "Bicycles" and "Repairing", and combines them with a given syntax
> like "Bicycles--Repairing" to index a particular document.
> Post-coordination on the other hand is performed as part of an
> information retrieval task. For example if a given document is indexed
> with two distinct concepts "Bicycles" and "Repairing" and a user
> decides to perform a search for all documents that are indexed with
> "Bicycles" and "Repairing".
> SKOS has some facilities for representing concept coordination. The
> most basic form of pre-coordination is certainly expressible with
>   ex:bicycleRepair a skos:Concept ;
>       skos:prefLabel "Bicycle Repair"@en .
> Post-coordination as an information retrieval activity also lends
> itself to representation as a SPARQL query. For example, given two
> distinct concepts:
>   ex:bicycles a skos:Concept ;
>       skos:prefLabel "Bicycles"@en .
>   ex:repairing a skos:Concept ;
>       skos:prefLabel "Repairing"@en .
> you could construct a SPARQL query to return only the documents that
> are indexed with both concepts:
>   SELECT ?document
>   WHERE {
>     ?document dc:subject ex:bicycles .
>     ?document dc:subject ex:repairing .
>   }
> However the SKOS vocabulary itself does not provide any mechanism for
> expressing that a given concept consists of a pre-coordination of
> other concepts. Of course it is perfectly feasible to extend SKOS [3]
> to establish a pattern for representing coordinated concepts. For
> example it has been suggested [4] that a new property such as
> <code>ex:coordinationOf</code> could be established:
>   ex:coordinationOf a rdf:Property ;
>     rdfs:domain skos:Concept ;
>     rdfs:range rdf:List .
> Which could then be used in assertions such as:
>   ex:bicyclesRepairing a skos:Concept ;
>       ex:coordinationOf (ex:bicycles, ex:repairing) ;
>       skos:prefLabel "Bicycles--Repairing"@en .
> It has also been suggested that OWL itself could be used to coordinate concepts:
>   ex:bicyclesRepairing a skos:Concept ;
>       owl:unionOf (ex:bicycles, ex:repairing) ;
>       skos:prefLabel "Bicycles--Repairing"@en.
> However, established patterns for pre-coordinations of this kind have
> not yet emerged in the SKOS community. <code>ex:coordinationOf</code>
> (or some equivalent extension), and the ramifications of using SKOS
> with OWL [5] have not been explored fully enough yet to warrant
> inclusion in the SKOS Reference [6], and consequently in this Primer.
> Rather than commit to a design pattern that hasn't been proven useful,
> the Semantic Web Deployment Group decided to postpone the issue of
> coordination [7], to allow extension patterns to organically emerge as
> SKOS is deployed. The hope is that as successful patterns are
> established they can be documented as a W3C Note or some equivalent.
> @@ TODO include info about wiki/discussion list here or in
> Specialization section? @@
> [1] http://www.willpowerinfo.co.uk/glossary.htm#pre-coord
> [2] http://www.willpowerinfo.co.uk/glossary.htm#post-coord
> [3] http://www.w3.org/TR/skos-primer/#secskosspecialization
> [4] http://isegserv.itd.rl.ac.uk/public/skos/press/dc2006/coordination.html
> [5] http://www.w3.org/TR/skos-primer/#secskosowl
> [6] http://www.w3.org/TR/skos-reference/
> [7] http://www.w3.org/2006/07/SWD/track/issues/40
Received on Tuesday, 19 August 2008 10:32:14 UTC

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