Re: Where DAML+OIL deviates from the RDF-Schema spec.

On Mon, 5 Mar 2001, Peter F. Patel-Schneider wrote:

> Sorry I should have made my comments more precise.
> 
> However, I think that my point still stands.  There is no statement in RDFS
> that subClassOf is < (strict subset) and not <= (non-strict subset).  In
> the absence of such a statement, I think that the reading for subClassOf
> should be taken to be permissive.

No, they don't say that subClassOf implies strict subset. But they say the
everything else, and the interpretation is quite clear to me.
 
> It turns out, of course, that RDF and RDFS have no means of creating two
> classes that are equivalent, aside from subClassOf cycles, so, perhaps, the
> prohibition on cycles could be inferred to mean strict subset.

The spec says that

	"rdfs:subClassOf property is transitive"

and a line or so below that they continue

	"A class can never be declared to be a subclass of itself, nor
	of any of its own subclasses. Note that this constraint is not
	expressible using the RDF Schema constraint facilities
	provided below, and so does not appear in the RDF version of
	this specification given in Appendix A"

It is obvious for me what this means, and why it is there.

> However, this is, in my opinion, ``reading between the lines'', and
> any clarification would be a change.

Well, we agree on one thing, namely that this could have been
formulated more clearly. Anyway, only a negligible amount of reading
between the lines is required to spot the difference between daml and
rdfs in this respect. As a first approximation I'd say that this
amount could be regarded as zero.
 

Sigge

Received on Monday, 5 March 2001 10:53:32 UTC