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Re: cycles in subclass hierarchy (was: RDFCore Update)

From: Wolfgang Nejdl <nejdl@kbs.uni-hannover.de>
Date: Thu, 13 Sep 2001 19:59:55 +0200
Message-Id: <200109131759.f8DHxt401965@liszt.kbs.uni-hannover.de>
To: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
cc: www-rdf-logic@w3.org
> 
> Brian McBride <bwm@hplb.hpl.hp.com> wrote:
> 
> > The minutes of the RDFCore WG face to face meeting
> > 
> >   http://www.w3.org/2001/sw/RDFCore/20010801-f2f/
> > 
> > have just been approved 
> 
> The following is a summary of the discussion in the DAML+OIL joint
> committee as input to the decision on allowing cycles in the RDFS 
> class hierarchy or not.
> 
> The message is: allowing cycles is mandatory for DAML+OIL, and not
> allowing them in RDFS will seriously break the layering of the
> Semantic Web architecture.
> 

...

> 6. An important design rationale behind DAML+OIL (and in fact much other
> stuff on the Semantic Web so far) has been a layered approach, where
> languages are stacked on top of each other, with as much partial
> interpretation between the layers as possible. Tim BL has even argued in
> [1], [2], [3] and many other places that such "partial understanding is
> an essential design principle of the Web in general, Semantic or not.
> 
> The decision to make rdfs:subClassOf acyclic will force DAML+OIL to
> introduce daml:subClassOf, and will therefore lead to an almost total
> loss of partial understanding between these two closely related ontology
> languages...
> 

Yes. Just to add my comments (very much supporting these arguments):
The main contribution of RDFS to RDF is the definition of
rdfs:subclassof and its interaction with rdf:type. If DAML+OIL could
not reuse rdfs:subclassof, there is basically nothing left from RDFS,
which is reused in DAML+OIL.

Wolfgang

> Frank van Harmelen.
>                  ----
> Frank.van.Harmelen@cs.vu.nl              http://www.cs.vu.nl/~frankh
> Department of AI, Faculty of Sciences,  Vrije Universiteit Amsterdam
> de Boelelaan 1081a, 1081HV Amsterdam, The Netherlands
> tel (+31)-20-444 7731 fax&voicemail (+31)-84-8722806
> 
> [1] Evovability, WWW7 keynote speach,
>     http://www.w3.org/DesignIssues/Evolution.html 
> [2] "Web Architecture from 50,000 feet"
>     http://www.w3.org/DesignIssues/Architecture.html
> [3] "Web Architecture: Extensible languages"
>     http://www.w3.org/DesignIssues/Extensible.html


--
Prof. Dr. Wolfgang Nejdl              tel. +49 511 762-19710
Institut für Technische Informatik    fax. +49 511 762-19712
Rechnergestützte Wissensverarbeitung  http://www.kbs.uni-hannover.de/
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Received on Thursday, 13 September 2001 14:00:11 UTC

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