Re: rdfs:Class vs. daml:Class ?

On Fri, 2002-03-15 at 16:01, Ian Horrocks wrote:
> On March 15, David Martin writes:
> > > I understand from the Pan and Horrocks paper at
> > >
> > > 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.

Ian, please be clear that this is your personal opinion of DAML+OIL,
not the consensus of the group that designed it.

I don't want this property.

I consider the design unfinished, as we agreed 20 Feb 2001:

  RESOLVED: We will release an updated language release
  incorporating the current proposal, acknowledge the outstanding
  issues and concerns, and solicit feedback from the larger


I'm quite disappointed that the concerns weren't actually
acknowledged in the spec that was released.

Meanwhile, there are two different formalizations of DAML+OIL:
    *  model-theoretic-semantics.html -
       revised Model-Theoretic Semantics
    * axiomatic-semantics.html - revised Axiomatic Semantics
        (from August 2001)

Note the axiomatic semantics doesn't have this bug involving separation
of datatypes from the rest of the universe of discourse.

> 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.

Or never use it. I don't think it's useful.

> I hope I explained why there are two.

Dan Connolly, W3C

Received on Friday, 29 March 2002 10:06:15 UTC