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RE: [OWLWG-COMMENT] ISSUE-55 (owl:class)

From: Michael Schneider <schneid@fzi.de>
Date: Thu, 20 Dec 2007 09:40:41 +0100
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A05A5ED3@judith.fzi.de>
To: "Alan Ruttenberg" <alanruttenberg@gmail.com>
Cc: "Owl Dev" <public-owl-dev@w3.org>, <pfps@research.bell-labs.com>

Hi again, Alan!

Alan Ruttenberg wrote on Monday, December 10:

>Here's my understanding of the situation (if I've got it wrong  
>somewhere, please correct me).
>
>On Dec 8, 2007, at 3:20 PM, Michael Schneider wrote:
>
>> But, AFAICS, this would only become a real problem, if in this  
>> ontology some class is used as an individual (metamodelling).
>
>Or if the class has instances that are literals.
>
>> But in such a case, even after changing rdfs:Class to owl:Class,  
>> the resulting ontology would still be an OWL-Full ontology: There  
>> would, for example, be an 'rdf:type' triple with some class being  
>> at the individual position, or a class with an object or 
>data property
>> attached.
>
>The type triple is inferred in OWL Full - it doesn't have to be  
>explicit.
>
>> The OWL-DL reasoner would refuse to work in such a situation, of  
>> course.
>
>Because the triple would sometimes need to be inferred by the  
>reasoner itself, the DL reasoner can't detect the situation in all  
>cases. Strictly speaking, it can only detect the case where it  
>certainly shouldn't work.
>
>> So it looks to me that this recommendation is safe.
>
>I would say, no. However it might be ok if the user was warned, or  
>made an explicit declaration to that effect.

Looks like things have changed, because Peter has found a way to make the
difference "perceivable":

  <http://lists.w3.org/Archives/Public/public-owl-wg/2007Dec/0227.html>

The trick is to force owl:Thing to be a /finite/ class (in Peter's ontology
owl:Thing happens to equal the union of the two defined classes, which are
both finite). In OWL-Full owl:Thing is always infinite, while it may be
finite in OWL-DL. 

@Peter: However, please consider Jeremy's ISSUE-73 in this context:

  <http://www.w3.org/2007/OWL/tracker/issues/73>

What I cannot tell is whether this is a show stopper for the "rdfs:Class
repair" or not. I wouldn't believe so, but I have to ponder about this
further.

Btw, I think the task of forcing owl:Thing to be a finite set can be even
easier achieved by simply making owl:Thing equivalent to some enumeration
class.

Cheers,
Michael

--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
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Email: Michael.Schneider@fzi.de
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Received on Thursday, 20 December 2007 08:40:56 GMT

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