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Antwort: Re: Fwd: logics of RDF

From: <ruediger.klein@daimlerchrysler.com>
Date: Thu, 31 Jan 2002 20:30:15 +0100
To: pfps@research.bell-labs.com
Cc: www-webont-wg@w3.org
Message-id: <0057440005001736000002L462*@MHS>
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 14:30:31 GMT

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