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

From: Michael Schneider <schneid@fzi.de>
Date: Sun, 9 Dec 2007 12:43:02 +0100
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A05A57E6@judith.fzi.de>
To: "Hans Teijgeler" <hans.teijgeler@quicknet.nl>
Cc: "Owl Dev" <public-owl-dev@w3.org>, <hendler@cs.rpi.edu>, <alanruttenberg@gmail.com>, <boris.motik@comlab.ox.ac.uk>, <pfps@research.bell-labs.com>, <ian.horrocks@comlab.ox.ac.uk>, <dlm@ksl.stanford.edu>

Hi, Hans!

>-----Original Message-----
>From: public-owl-dev-request@w3.org 
>[mailto:public-owl-dev-request@w3.org] On Behalf Of Hans Teijgeler
>Sent: Saturday, December 08, 2007 6:42 PM
>To: Michael Schneider
>Cc: 'Owl Dev'; hendler@cs.rpi.edu; alanruttenberg@gmail.com; 
>boris.motik@comlab.ox.ac.uk; pfps@research.bell-labs.com; 
>ian.horrocks@comlab.ox.ac.uk; dlm@ksl.stanford.edu
>Subject: RE: [OWLWG-COMMENT] ISSUE-55 (owl:class)
>Hi Michael,
>Clear analysis, 


> perhaps with some conflicting statements:
>1) "If one creates a new OWL ontology, one always should use 
>instead of 'rdfs:Class'";
>2) "Assume 'rdfs:Class' in RDFS ontologies, assume 'owl:Class' in OWL
>3) "OWL-Full is meant to be a semantic extension to RDFS. 
>Thus, in OWL-Full
>owl:Class is the same as rdfs:Class."  
>So what's the final outcome?
>We have built, and are still building, OWL ontologies in which 
>chains are possible.
> So we deal with OWL Full. 

Yes, in fact!

So be it.
>But does this mean that we'd have to change owl:Classes back to

No, you don't have to (although you are allowed to do so because in OWL-Full
owl:Class is the same as rdfs:Class). I argued for quite the opposite: If
you have rdfs:Classes in your OWL-Full ontology, then you may/should change
every occurrence of 'rdfs:Class' to 'owl:Class'! 

>following the rationale:
>- "OWL Full is a semantic extension of RDFS";

This is true...

>- hence an OWL Full ontology is an RDFS ontology;

No, I think this is a misunderstanding. It is the other way around: Every
RDFS ontology is also an OWL-Full ontology (formally a little broken,
because RDFS ontologies miss an OWL ontology header, but this is not
relevant for our semantics related discussion here).

When I said that OWL-Full is a semantic extension to RDFS, then I meant that
OWL-Full knows about all semantic conditions of RDFS, as given in the RDF
semantics spec, but OWL-Full also introduces additional semantic conditions
which are unknown to RDFS. These semantic conditions determine the set of
entailments you receive from a given ontology. So for a given RDFS ontology,
OWL-Full semantics will result in (at least) all entailments which you would
get from RDFS semantics.

>- "assume rdfs:Class in RDFS ontologies" ?
>Or am I completely off-track?

As long as you produce OWL ontologies (Lite, DL or Full), it is perfectly
save to use 'owl:Class' in all situations. This was the message of my
previous mail. So you never have to wonder about when to use 'rdfs:Class'
and when not. And people using your ontology do not have to wonder about
your intentions behind the use of 'rdfs:Class', when they find it being used
in certain places of your ontology. There will always only be 'owl:Class'.
Or as Bob Marley would express it: "No rdfs:Class, no cry!" ;-)

Only if you really intend to produce genuine RDFS ontologies, then you need
to use 'rdfs:Class', because RDFS reasoners do not know about 'owl:Class'. 

So just go on with using 'owl:Class' everywhere in all your OWL ontologies,
and you will always be on the right track! :)



Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: Michael.Schneider@fzi.de
Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555

FZI Forschungszentrum Informatik an der Universität Karlsruhe
Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
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Received on Sunday, 9 December 2007 11:43:22 UTC

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