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RE: ISSUE-55 (owl:class): owl:class v. rdfs:class

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Tue, 13 Nov 2007 14:08:27 +0900
To: "'OWL Working Group WG'" <public-owl-wg@w3.org>
Message-ID: <000001c825b3$3f000a00$8f63dcd3@wolf>

Hello,

Changing rdfs:Class into owl:Class does significantly affect the formal meaning of an ontology. For example, owl:complementOf
complements the extension of owl:Class, but not of rdfs:Class. If necessary, I can come up with examples in which satisfiability of
an ontology changes if you change rdfs:Class to owl:Class.

I know what people will say: in many practical cases, such corner-case changes in the semantics won't affect the ontology
significantly. Still, it might be a good idea to keep the definition of the language clean so that we know how exactly to interpret
an ontology.

Changing an rdfs:Class to owl:Class is something that can be done by an implementation to "repair" an ontology. However, this is
then something an implementation may choose to do, and the implementation is then responsible for knowing what it is doing.

In contrast, putting something like this into the language itself opens a whole can of worms. It would make the definition of the
semantics difficult, and it would make it establishing the precise relationship between the OWL DL and the OWL Full semantics quite
difficult, if not impossible.

We can put something like this into a separate FAQ or "Common Practices" document. I believe it might be quite helpful for tool
developers.

Regards,

	Boris

> -----Original Message-----
> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of OWL Working
> Group Issue Tracker
> Sent: 13 November 2007 12:42
> To: public-owl-wg@w3.org
> Subject: ISSUE-55 (owl:class): owl:class v. rdfs:class
> 
> 
> 
> ISSUE-55 (owl:class): owl:class v. rdfs:class
> 
> http://www.w3.org/2007/OWL/tracker/issues/
> 
> Raised by: James Hendler
> On product:
> 
> At ISWC 07, it has come up in several presentations that a great many OWL Full ontologies (in RDFS
> esp) become OWL DL if you just change rdfs:class to owl:class - while it is acknowledged that this
> makes a semantic change, many people said they simply just do it in their tools.
> 
> 
> Given the improved understanding at this point of things like punning, the WG might want to revisit
> this issue and see if there is a technical solution that could be considered - or at least make a
> clear and precise statement as to why we are unable to do so and why this dichotomy must consider to
> exist (as unfortunate as that is)
> 
> 
> 
> 
Received on Tuesday, 13 November 2007 05:09:22 GMT

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