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Re: owl:Thing in RL profile?

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Thu, 13 Aug 2009 10:31:47 +0100
Message-Id: <2919A3C7-EE13-4A6F-9828-39A590909D30@comlab.ox.ac.uk>
Cc: "'W3C OWL Working Group'" <public-owl-wg@w3.org>
To: Boris Motik <boris.motik@comlab.ox.ac.uk>
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
>
>> -----Original Message-----
>> From: Michael Schneider [mailto:schneid@fzi.de]
>> Sent: 12 August 2009 23:44
>> To: mak@aifb.uni-karlsruhe.de
>> Cc: W3C OWL Working Group; Bernardo Cuenca Grau; Boris Motik; Ian  
>> Horrocks;
>> Zhe Wu; Achille Fokoue
>> Subject: RE: owl:Thing in RL profile?
>>
>> Hi!
>>
>> Markus Krötzsch wrote:
>>
>>> Bothering you again with the below question. If this is a bug we  
>>> should
>>> probably get it fixed soon. -- Markus
>>>
>>> On Samstag, 8. August 2009, Markus Krötzsch wrote:
>>>> The forwarded email below asks the question whether assertions  
>>>> of the
>>>> form
>>>>
>>>> ClassAssertion(owl:Thing auto)
>>>>
>>>> are allowed in OWL RL. They seem to be excluded by the grammar, but
>>>> maybe this is a bug rather than deliberate design.
>>
>> Hm, maybe I'm missing something (it's much too late in the day,  
>> literally
>> :)), but it looks to me that this would break theorem PR1 [1]. For  
>> example,
>> look at the graphs
>>
>> G1 := {
>>   ex:o rdf:type owl:Ontology .
>>   ex:drivenBy rdf:type owl:ObjectProperty .
>>   ex:auto ex:drivenBy ex:alice .
>> }
>>
>> G2 := {
>>   ex:o rdf:type owl:Ontology .
>>   ex:auto rdf:type owl:Thing .
>> }
>>
>> With owl:Thing being allowed to appear as classes in class  
>> assertions, the
>> reverse RDF mappings for both G1 and G2 would be in the OWL 2 RL  
>> syntactic
>> fragment, and the pair <G1,G2> would satisfy the premises of PR1.  
>> Further,
>> G1 direct entails G2. But G2 cannot be inferred from G1 via the  
>> OWL 2 RL/RDF
>> rules.
>>
>> Of course, this could as well be considered a problem with PR1, or  
>> with the
>> RL/RDF rules...
>>
>> Good night,
>> Michael
>>
>> [1] <http://www.w3.org/2007/OWL/wiki/Profiles#Theorem-PR1>
>>
>>>> If not, we need to revisit
>>>> profile classifications of some test cases.
>>>>
>>>> Feedback (esp. by the Profiles editors) is welcome.
>>>>
>>>> Thanks,
>>>>
>>>> Markus
>>
>> --
>> Dipl.-Inform. Michael Schneider
>> Research Scientist, Dept. Information Process Engineering (IPE)
>> Tel  : +49-721-9654-726
>> Fax  : +49-721-9654-727
>> Email: michael.schneider@fzi.de
>> WWW  : http://www.fzi.de/michael.schneider
>> ===================================================================== 
>> ==
>> FZI Forschungszentrum Informatik an der Universität Karlsruhe
>> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
>> Tel.: +49-721-9654-0, Fax: +49-721-9654-959
>> Stiftung des bürgerlichen Rechts, Az 14-0563.1, RP Karlsruhe
>> Vorstand: Prof. Dr.-Ing. Rüdiger Dillmann, Dipl. Wi.-Ing. Michael  
>> Flor,
>> Prof. Dr. Dr. h.c. Wolffried Stucky, Prof. Dr. Rudi Studer
>> Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
>> ===================================================================== 
>> ==
>
>
>
Received on Thursday, 13 August 2009 09:34:30 GMT

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