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Re: some thoughts about ISSUE 35 ConceptSchemeContainment

From: Sean Bechhofer <sean.bechhofer@manchester.ac.uk>
Date: Wed, 8 Aug 2007 10:41:40 +0100
Message-Id: <6C72011B-8E7E-4EE3-BE91-A5247B34C6F5@manchester.ac.uk>
Cc: Daniel Rubin <dlrubin@stanford.edu>, Guus Schreiber <schreiber@cs.vu.nl>, SWD WG <public-swd-wg@w3.org>, SKOS <public-esw-thes@w3.org>
To: Antoine Isaac <aisaac@few.vu.nl>

On 26 Jul 2007, at 08:04, Antoine Isaac wrote:

>
> Hello,
>
> I'm sorry for being picky once again, but I disapprove of almost  
> all this, mainly for useability reasons:
>
> 1. using owl:ontology as a substitute for skos:ConceptScheme is  
> dangerous, because people will confuse concepts with class even  
> more than what is now. We'll need to document this extensively,  
> possibly using the idea of ConceptScheme again, so I'm worried.
>
> 2. owl:imports defines importing on an ontology basis: if you want  
> to import just some concepts and/or if you want to change the links  
> between them to have your own view on the domain, you're going into  
> a mess
>
> 3. as I already mentioned discussing with Alistair on using complex  
> algorithms to handle his solution for concept grouping, I  
> disapprove of all that could make one user's life a hell. And I  
> think relying on querying (vs. explicit representation) for  
> accessing all kind of needed information harms the use of the  
> model. Take the example of the RDFS query engines that have  
> implemented a predicate like "directSubClassOf" to access direct  
> link between classes (which you can do by making your query just a  
> little bit more comple) : there must be a reason...
>
> 4. finally I'm sceptical about the use of namespaces or RDF-based  
> solutions for provenance/trust (like quadruples or named graphs) to  
> handle concept scheme information. To me these are based on  
> knowledge source (that we trust or not, etc.) and I think there is  
> no bijection between a knowledge source and a concept scheme: a  
> same source could provide information about several concept schemes  
> and different (trusted) sources could contribute to define a same  
> scheme. I don't say that's impossible, I just want to warn that  
> this call for thinking about different cases and solutions, as well  
> as writing pages of guidelines that we might not have the time for.

When we were discussing the containment issue during yesterday's
telecon, there was talk of using the namespace to determine whether a
concept is part of a scheme. In other words, if I have concept

http://example.com/scheme#Car

then that concept is "in" the scheme

http://example.com/scheme

As Guus (I think) said, and Antoine points out above, this is a
convention that we often see in OWL ontologies. However, it is just a
*convention*, and there is nothing in the language that stops me from
declaring classes with URIs from different namespaces within that
scheme. I would be wary of relying on this mechanism unless we give
very strong guidance/rules as to the URIs that one can use or define
within a scheme.

In the early days of OWL, there was much confusion over the difference
between namespace declarations and ontology import. A common cause of
errors (e.g. see [1]) was that users often thought that by declaring a
namespace, they had "imported" the classes and properties that were in
that namespace. I'd like to avoid reintroducing that kind of
confusion.

	   Sean

[1] Patching Syntax in OWL Ontologies http://dx.doi.org/10.1007/b102467

--
Sean Bechhofer
School of Computer Science
University of Manchester
sean.bechhofer@manchester.ac.uk
http://www.cs.manchester.ac.uk/people/bechhofer
Received on Wednesday, 8 August 2007 10:02:16 GMT

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