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Re: Antwort: Re: Fwd: logics of RDF

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 31 Jan 2002 14:14:04 -0500
To: ruediger.klein@daimlerchrysler.com
Cc: www-webont-wg@w3.org
Message-Id: <20020131141404C.pfps@research.bell-labs.com>
Unfortunately, RDFS has precisely the class that prevents layering,
rdfs:Class.  Modifying RDFS to a layered theory might help, but this would
be a significant modification of RDFS, as much of the justification for
RDFS is precisely that it has classes like rdfs:Class.

peter


From: ruediger.klein@daimlerchrysler.com
Subject: Antwort: Re: Fwd: logics of RDF
Date: Thu, 31 Jan 2002 20:06:42 +0100

> Hi Peter:
> 
> thanks for your quick response!
> 
> I had some problems to interpret the syntax in your (and Dieter's and Ziv's) 
> OWL-RDF layering document.
> 
> If such elementary paradoxa are the trouble  - isn't there a chance to modify 
> RDF according to some more elaborated theories? For instance, instead of naive 
> set theory with Russell's paradoxon a axiomatic set theory with layered sets ? 
> It would NOT cause - I think - any practical consequences to re-define rdf:type 
> in such a way that it follows a layered type concept. And it would help us (!) 
> to define OWL in a more RDF compatible way.
> 
> Ruediger
> 
> 
> 
> 
> 
> 		
> 	pfps@research.bell-labs.com
> 	31.01.02 19:32
> 	Bitte antworten an pfps
> 	
> 	
> 		 
> 		 An: dieter@cs.vu.nl
> 		 Kopie: Ruediger Klein/FT/DCAG/DCX@WK-EMEA2
> 		 Thema: Re: Fwd: logics of RDF
> 
> Hi Ruediger:
> 
> Think of the initial version of set theory.
> 
> In this set theory, there are a (very large) collection of built-in sets.
> All set theories include these built-in sets, and usually many more.
> Unfortunately, this collection includes
> 
>  { x : x not an element of x }
> 
> which violates the implicit assumption that the set membership
> relationship is well-defined, resulting in no models for any collection of
> sets built on this set theory.
> 
> OWL layered on top of RDFS as a same-syntax extension has the same problem.
> There would have to be a large collection of built-in restrictions in any
> KB.  Unfortunately, this collection includes the restriction that is
> defined as those resources that do not belong to the restriction.  The
> rdf:type relationship is ill-defined on this restriction, resulting in no
> models for any OWL KB.
> 
> RDF(S) does not fall into this paradox because it does not need a large
> collection of built-in classes.
> 
> peter
> 
> 
> 
> 
> From: Dieter Fensel <dieter@cs.vu.nl>
> Subject: Fwd: logics of RDF
> Date: Thu, 31 Jan 2002 19:22:37 +0100
> 
> >
> > >From: <ruediger.klein@daimlerchrysler.com>
> > >To: <dieter@cs.vu.nl>
> > >Subject: logics of RDF
> > >Date: Thu, 31 Jan 2002 19:10:03 +0100
> > >
> > >Hallo Dieter:
> > >
> > >I'm not sure if I really understood in your OWL-RDF layering email what the
> > >logical problems with RDF are. Obviously one can represent logically
> > >inconsistent things in RDF. Why? Is that something irrelevant in RDF because
> > >logical inconsistency is not a notion in RDF?
> > >
> > >Why did the RDF people allow such things in RDF? Does it have any advantages
> > >within that framework?
> > >If logical inconsistency is also a problem within the RDF framework
> > >itself, is
> > >there a chance (from a technical point of view) to re-formulate it in such a
> > >way that logical inconsistency can be avoided?
> > >Is there also a chance from a political point of view?
> > >
> > >Can you, please, try to BRIEFLY comment on this?
> > >
> > >Thanks a lot
> > >
> > >Ruediger
> > >
> > >(If you know anybody who can do it, please simply forward my email -
> > >that's why
> > >it comes in English)
Received on Thursday, 31 January 2002 14:15:25 GMT

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