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Re: WOWG: agenda Aug 15 telecon

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 15 Aug 2002 13:50:48 -0700
Message-Id: <p05111b0ab981c363ed6d@[]>
To: Jim Hendler <hendler@cs.umd.edu>
Cc: www-webont-wg@w3.org

>At 8:28 AM -0400 8/15/02, Peter F. Patel-Schneider wrote:
>>From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
>>Subject: Re: WOWG: agenda Aug 15 telecon
>>Date: Thu, 15 Aug 2002 13:58:37 +0200
>>>  Further to my summary of the contributions to public comments list,
>>>  two new messages arrived today, both of which are also relevant to the
>>>  semantics discussion also on the agenda for today:
>>>  Message [1] points out a bug in the DAML+OIL spec that we are about to be
>>>  bitten by as well if we don't take care. (Essentially the current DAML+OIL
>>>  spec of sameClassAs forces its arguments to be of type daml:Class,
>>  > even if without that statement they would only be of type rdfs:Class).
>To the best of my recollection, the discussion of the precise 
>differences between daml:class and rdfs:class, which seems to carry 
>over into our current decision-making and issues, was discussed in 
>the DAML joint committee, and not really in this WG -- I've looked 
>through the archives and seen many references to owl:class being 
>different than rdfs:class, but I cannot find a message that 
>precisely describes the differences -- can someone either point the 
>WG to such a message (or import one from joint-committee WG 
>archives) or write a summary.  From our own discussions, it is not 
>clear to me what is being offered as a reason not to simply drop 
>owl:class and use rdfs:class (or just make them equivalent if we 
>resolve the open issue to have everything be owl:)
>  -JH

When DAML was written, there was a bug in the rdfs:Class spec. Now 
that has been fixed, we can rationally assert

daml:Class rdfs:subClassOf rdfs:Class .

but not the reverse, because RDFS allows classes which violate DAML 
(and OWL) ground assumptions, eg classes that contain literals, 
classes that contain themselves, things like that.

Now, if OWL weren't in the powerful grip of the description 
logicians, we *could* have designed it to be as liberal as RDFS, and 
just used rdfs:Class in OWL. Hey ho.


>Professor James Hendler				  hendler@cs.umd.edu
>Director, Semantic Web and Agent Technologies	  301-405-2696
>Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
>Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)

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Received on Monday, 19 August 2002 12:25:53 UTC

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