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Re: rdfs:Class vs. daml:Class ?

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Tue, 19 Mar 2002 13:41:14 +0000
Message-ID: <15511.16378.67911.727519@oaklands.demon.co.uk>
To: www-rdf-logic@w3.org
On March 18, Steven Gollery writes:
> Ian,
> 
> Thank you for the explanation. I realized after writing the original message that it was
> basically only a coincidence that the majority of DAML ontologies I was working with
> were using rdfs:Class: I see now that only some of the ontologies on the list at the
> DAML site do this and the majority use daml:Class.
> 
> About your paper: has there been any official response to the idea of using rdfs(fa) to
> redefine the model for rdf and rdfs?

Not much. There is a proposal to indicate some triples as being
"non-asserted", which I believe can be seen as a very weak form of
layered architecture (but when I suggested this to Pat he was rather
dismissive).

Ian

> 
> Thanks again,
> 
> Steve Gollery
> 
> Ian Horrocks wrote:
> 
> > On March 15, David Martin writes:
> > > I think some clarification of this question would be helpful to others of us as
> > > well.  I was eager to read the Pan and Horrocks paper mentioned below, but the URL
> > > is broken:
> > >
> > > Not Found
> > > The requested URL /jpan/Zhilin/download/Paper/Pan-Horrocks-rdfsfa-2001.pdf was not
> > > found on this server.
> > > Apache/1.3.9 Server at imgcs.cs.man.ac.uk Port 80
> > >
> > > Can someone please post a working URL for this paper?
> >
> > Sorry, but they just moved to a new server and everything is still a
> > bit wobbly. You can get the paper from my site on different server:
> >
> > http://www.cs.man.ac.uk/~horrocks/Publications/download/2001/rdfsfa.pdf
> >
> > I suppose that while writing I should try to answer Steven's question:
> >
> > >
> > > Thanks,
> > >
> > > David
> > >
> > > Steven Gollery wrote:
> > >
> > > > Please excuse another naive newby question....
> > > >
> > > > In the DAML language definition, it looks like rdfs and rdf are being
> > > > used as the metamodel: daml:Class, for example, is an instance of
> > > > rdfs:Class. But if that is the case, I would expect that the Class
> > > > definitions in a DAML ontology would be instances of daml:Class.
> > > > Instead, the sample ontologies that I've seen use rdfs:Class either
> > > > exclusively or (as far as I can tell) interchangeably with daml:Class.
> >
> > You are right that in many cases rdf is being used as the "metamodel"
> > (i.e., to describe the DAML+OIL language itself), but things are a
> > little confused as some parts of rdf are used directly in DAML+OIL,
> > e.g., range and domain, subClassOf.
> >
> > > >
> > > > I understand from the Pan and Horrocks paper at
> > > > http://img.cs.man.ac.uk/jpan/Zhilin/download/Paper/Pan-Horrocks-rdfsfa-2001.pdf
> > > > that there is a layering problem in the RDF/RDF(S) definition that
> > > > prevents a clean division between successive metamodel levels. Is the
> > > > relationship between rdfs:Class and daml:Class somehow connected to
> > > > this?
> >
> > More or less. The extension of a DAML+OIL class should be a set of
> > individuals (well, strictly a set of objects that are denoted by
> > individual names) and not, say, a set of properties, as could be the
> > case for an rdfs:Class. Because of the lack of layering in the rdf
> > architecture there is no way to enforce this, so daml:Class is just a
> > label given to the subset of rdfs:Classes that have the property we
> > want. Note that in the daml+oil-ex.daml file, daml:Class is used
> > extensively. Also note that many of the "meta" properties in the daml
> > language definition have daml:Class as a range/domain so that classes
> > used in daml ontology will often be implicitly of type daml:Class.
> >
> > > >
> > > > I suppose all I'm really asking is: when would I use rdfs:Class and when
> > > > would I use daml:Class? And if it doesn't matter, why are there two of
> > > > them?
> >
> > Always use daml:Class. I hope I explained why there are two.
> >
> > Ian
> >
> > > >
> > > > Thanks for your patience,
> > > >
> > > > Steven Gollery
> 
Received on Tuesday, 19 March 2002 08:43:05 GMT

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