W3C home > Mailing lists > Public > public-owl-wg@w3.org > August 2009

RE: owl:Thing in RL profile?

From: Michael Schneider <schneid@fzi.de>
Date: Thu, 13 Aug 2009 11:51:20 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A0015DE2EC@judith.fzi.de>
To: "Ian Horrocks" <ian.horrocks@comlab.ox.ac.uk>, "Boris Motik" <boris.motik@comlab.ox.ac.uk>
Cc: "W3C OWL Working Group" <public-owl-wg@w3.org>
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)
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Email: michael.schneider@fzi.de
WWW  : http://www.fzi.de/michael.schneider
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Received on Thursday, 13 August 2009 09:52:01 GMT

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