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Re: rdfs:Class vs. daml:Class ?

From: Steven Gollery <sgollery@cadrc.calpoly.edu>
Date: Mon, 18 Mar 2002 08:46:49 -0800
Message-ID: <3C9619F8.B12C182D@cadrc.calpoly.edu>
To: www-rdf-logic@w3.org
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?

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 Monday, 18 March 2002 11:46:16 GMT

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