W3C home > Mailing lists > Public > www-webont-wg@w3.org > January 2003

RE: ISSUE: owl:Class name misleading; try owl:Set?

From: Dan Connolly <connolly@w3.org>
Date: 02 Jan 2003 18:44:56 -0600
To: Jim Hendler <hendler@cs.umd.edu>
Cc: Ziv Hellman <ziv@unicorn.com>, Jeff Heflin <heflin@cse.lehigh.edu>, "Peter F. "Patel-Schneider <pfps@research.bell-labs.com>, www-webont-wg@w3.org
Message-Id: <1041554696.19697.107.camel@dirk.dm93.org>

On Thu, 2003-01-02 at 17:12, Jim Hendler wrote:
> CHAIR'S NOTE
[...]
> 3. We made a decision at that owl:class is a subclass of rdfs:class 
> but not identical to rdfs:class (per closing of issue 5.22 and the 
> "semantic consensus"). The RDF Schema document [1] reads:
> 
> >RDF distinguishes between a class and the set of its instances. 
> >Associated with each class is a set, called the class extension of 
> >the class, which is the set of the instances of the class. Two 
> >classes may have the same set of instances but be different classes. 
> >For example, the tax office may define the class of people living at 
> >the same address as the editor of this document. The Post Office may 
> >define the class of people whose address has the same zip code as 
> >the address of the author. It is possible for these classes to have 
> >exactly the same instances, yet to have different properties. Only 
> >one of the classes has the property that it was defined by the tax 
> >office, and only the other has the property that it was defined by 
> >the Post Office.
> 
> so if we decided to go with a purely set based approach, the we would 
> not be a subset,

No? Please explain.

As far as I can tell, it's quite coherent to say that
the class of sets is a subclass of the class of classes.
That's what cyc does
http://www.cyc.com/cyc-2-1/vocab/math-vocab.html#Set-Mathematical

and KIF seems to do something similar... hmm...
taking another look, maybe this isn't relevant.
http://meta2.stanford.edu/kif/Hypertext/node24.html#SECTION00073000000000000000

But still... please explain why it's not OK to say
that owl:Set rdfs:subClassOf rdfs:Class?

>  but a different animal, and  we would have to reopen 
> this discussion and issue (which I'm not inclined to do).

> My belief at the moment is that Semantics is consistent with the RDF 
> S use of class, and thus I'm reluctant to introduce a different 
> semantics at this late date.

I don't think I'm introducing a different semantics. I think
I'm just suggesting a more clear name for what we've got.

>   I believe it would require a strong 
> (STRONG) consensus of the WG if the decision is made to change this 
> (esp. as the current also  seems to be consistent with DAML+OIL 
> according to Peter in [2]).
> 
> I may be misunderstanding the issue,

One of us is.

>  in which case I apologize, the 
> above are not meant to force a particular decision but to express 
> reluctance by the chair to introduce any major change on something 
> this basic.
> 
> -JH
> 
> 
> [1] http://www.w3.org/2001/sw/RDFCore/Schema/200212bwm/
> [2] http://lists.w3.org/Archives/Public/www-webont-wg/2003Jan/0011.html
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 2 January 2003 19:44:45 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:57:56 GMT