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Re: SKOS: COMMENT: Re: [Mulgara-general] Rules and SKOS

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Wed, 01 Oct 2008 13:08:45 +0200
Message-ID: <48E35A3D.7090903@few.vu.nl>
To: David Wood <david@zepheira.com>
CC: Mulgara General <mulgara-general@mulgara.org>, SKOS <public-esw-thes@w3.org>, SWD WG <public-swd-wg@w3.org>

Dear David,

I would add, as an editor of the Primer, that I'd be very interested 
also in hearing whether the section we had put in the Primer about this 
aspect [1] was unclear as well, especially the last note on "assumed 
transitivity". If yes, then we'll change it!

Thanks a lot for your feedback,

Antoine

[1] http://www.w3.org/TR/skos-primer/#sectransitivebroader
> Hi David,
>
> Thanks for forwarding this, this is great. This is also very timely,
> as we're within the last call comment period, so now is the time to
> speak if this work raises any issues.
>
> There is one issue which I would particularly appreciate feedback
> on. Looking at http://mulgara.org/trac/wiki/SKOS I see the following:
>
> """ 
> There is also a workaround in this definition file to deal with a
> peculiarity in SKOS.
>
> SKOS declares that skos:broader is a sub-property of
> skos:broaderTransitive. Similarly, skos:narrower is a sub-property of
> skos:narrowerTransitive. However, the documentation also declares that
> "sub-property" does not inherit transitivity. This means that
> skos:broader and skos:narrower do not have a rdfs:subPropertyOf
> relationship to skos:broaderTransitive and skos:narrowerTransitive.
> """
>
> Do you believe that the SKOS Reference misuses or misunderstands the
> notion of "sub-property" as defined in RDFS and OWL? If so, then that
> is a serious issue for us.
>
> The SKOS Reference defines the SKOS data model as an OWL Full
> ontology, with the standard OWL interpretations of sub-property and
> transitivity. As I understand RDFS and OWL, transitivity is not
> inherited by sub-properties of a transitive property. For example, the
> ancestor relationship is transitive, but sub-properties of ancestor
> such as father or grandmother are not transitive. Am I missing
> something?
>
> """
> To get around this, we've directly sub-classed
> skos:broader/skos:narrower off skos:semanticRelation, and removed
> their relationship to
> skos:broaderTransitive/skos:narrowerTransitive. We have also added in
> the explicit relationship:
>
> skos:broaderTransitive(A,B) :- skos:broader(A,B).
> """
>
> Again, based on my understanding of sub-properties and transitivity in
> OWL, I do not see why this workaround is necessary. If I've
> misunderstood, please do explain ASAP. If SKOS requires such a
> workaround then we should change it.
>
> Thanks again, and please do respond soon.
>
> Alistair.
>
>
> On Tue, Sep 30, 2008 at 07:53:52PM +0100, Simon Spero wrote:
>   
>> This is very interesting.
>>
>> This is also a very good example of just how the introduction of  
>> broaderTransitive and narrowerTransitive   may, on further reflection,  
>> turn out to be, upon further review, differently  weighted in the  
>> balancing of factors than, on ones initial impression, may have seemed, 
>> or rather, the converse.
>>
>> Or, to quote Professor Jane Greenberg, SKOS is neither Simple, or a  
>> K.O.S.
>>
>> Simon
>>
>>
>> On Sep 29, 2008, at 1:19 PM, David Wood wrote:
>>
>>     
>>> This is awesome, Paul!  Thanks!
>>>
>>> I'm copying the SKOS list so they know about it.
>>>
>>> Regards,
>>> Dave
>>>
>>> On Sep 28, 2008, at 7:26 PM, Paul Gearon wrote:
>>>
>>>       
>>>> I've recently had to do a little bit of work with SKOS and Rules, and
>>>> I thought it might be worth pointing out to people.
>>>>
>>>> You'll find a description on how to use rules in the Wiki at:
>>>> http://mulgara.org/trac/wiki/Rules
>>>>
>>>> I've also included a file for partial SKOS entailments (partial,
>>>> because I don't have collection support yet). This is attached to and
>>>> described in:
>>>> http://mulgara.org/trac/wiki/SKOS
>>>>
>>>> The SKOS rules may be informative for anyone wanting to use SKOS, or
>>>> rules in general. Note that almost all the work is done in the 6  
>>>> rules
>>>> at the bottom of the file. Everything else is done with OWL
>>>> vocabulary.  (There are 4 extra rules, some of which may be  
>>>> redundant,
>>>> plus a 5th that is necessary due to a strange requirement in SKOS,  
>>>> but
>>>> each of these are exceptional, rather than the norm).
>>>>
>>>> Regards,
>>>> Paul
>>>> _______________________________________________
>>>> Mulgara-general mailing list
>>>> Mulgara-general@mulgara.org
>>>> http://mulgara.org/mailman/listinfo/mulgara-general
>>>>         
>>>       
>>     
>
>   
Received on Wednesday, 1 October 2008 11:09:20 GMT

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