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Re: owl:Thing in RL profile?

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Thu, 13 Aug 2009 12:27:24 +0100
Message-Id: <FF53872F-D0ED-49B9-9A46-C15B139DB370@comlab.ox.ac.uk>
Cc: "Boris Motik" <boris.motik@comlab.ox.ac.uk>, "W3C OWL Working Group" <public-owl-wg@w3.org>
To: Michael Schneider <schneid@fzi.de>
I agree. Making changes here is non-trivial, and shouldn't be  
attempted at this stage.

Ian


On 13 Aug 2009, at 10:51, Michael Schneider wrote:

> The current situation is that starting from explicit typing triples
>
>   ex:C rdf:type owl:Class .
>   ex:w rdf:type ex:C .
>
> the RL/RDF rules provide
>
>   ex:C rdfs:subClassOf owl:Thing . // via rule scm-cls
>   ex:w rdf:type owl:Thing .        // via rule cax-sco
>
> But this does not follow without explicit typing.
>
> There are actually several RL rules treating owl:Thing and  
> owl:Nothing, but
> it's pretty incomplete support. But trying to change anything in  
> this late
> stage (after PR-voting!) would probably be a bit risky... :-)
>
> Michael
>
>> -----Original Message-----
>> From: public-owl-wg-request@w3.org [mailto:public-owl-wg- 
>> request@w3.org]
>> On Behalf Of Ian Horrocks
>> Sent: Thursday, August 13, 2009 11:32 AM
>> To: Boris Motik
>> Cc: 'W3C OWL Working Group'
>> Subject: Re: owl:Thing in RL profile?
>>
>> I agree with what Boris says. There are several features that we
>> excluded from RL on the grounds that they would hamper practical
>> implementation. I believe that this was one of them. The argument
>> goes that adding owl:Thing to the profile would require a rule that
>> adds the relevant type triple for every individual. Of course there
>> is nothing to prevent RL implementations from dealing correctly with
>> owl:Thing, but they are not required to do so in order to be  
>> conformant.
>>
>> Ian
>>
>>
>> On 13 Aug 2009, at 07:41, Boris Motik wrote:
>>
>>> Hello,
>>>
>>> I seem to remember that we explicitly excluded owl:Thing from OWL 2
>>> RL, on the
>>> account that it is difficult to support in OWL 2 RL/RDF. The
>>> objection there was
>>> that the extension of owl:Thing would become very large. As a
>>> consequence, the
>>> rules axiomatizing owl:Thing were removed from OWL 2 RL/RDF; but
>>> then, to make
>>> Theorem PR1 hold, we removed owl:Thing from OWL 2 RL as well.
>>>
>>> I'm not 100% sure of this, but it seems to me that this is what
>>> happened.
>>>
>>> Regards,
>>>
>>> Boris
>
> --
> Dipl.-Inform. Michael Schneider
> Research Scientist, Dept. Information Process Engineering (IPE)
> Tel  : +49-721-9654-726
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> Email: michael.schneider@fzi.de
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Received on Thursday, 13 August 2009 11:28:18 GMT

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