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

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

> > I belong to those that feel any set of sub-properties to a certain
> > property X, should not contain any property which is equivalent with X. 
> > This is like the distinction between less than or equal to '<=', or just
> > less than '<'. You want subPropertyOf and subClassOf to be like '<='. But
> > I want them to be like '<', for reasons similar to those put forward by
> > Ian and DanBri, among others.
> 
> If you want sub... to be <, then you have to make it be <.  Right now,
> there is no indication that sub... is indeed <.  In fact, there is no
> problem in RDF(S) having one class be a sub of another as well as
> equivalent to that other.  Adding this requirement would also be a change.

No, that is the requirement you see in RDFS, but not i DAML, First RDFS
states that: 

	The property rdfs:subPropertyOf is an instance of rdf:Property
	that is used to specify that one property is a specialization
	of another.

Which is the same as saying that one property has a  more narrow semantics.
Then RDFS continues

	A property can never be declared to be a subproperty of
	itself, nor of any of its own subproperties. 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.

This is a clear statement that the RDFS subpropertyof is related to
the DAML subpropertyof as is '<' related to '<='. I cannot see that
the RDFS way of thinking is flawed in any way, and being a down to
earth digital library kind of person I actually prefer
rdfs:subpropertyof to the daml:subpropertyof.
 
> > Your view is perfectly logical, as is that x1 <= x2 && x2 <= x1 implies
> > that x1 is equal to x2. However, I want subPropertyOf (X,Y) imply that Y
> > has a STRICTLY NARROWER semantics than X, and the same should go for
> > sameClassAs. 
> 
> Go ahead and argue for this, but it is as much of a change as eliminating
> the prohibition on cycles.

No it isn't, it is equivalent with preservering the prohibition on cycles,
and nothing else. Since it is the RDFS requirement of strictly narrower
semantics which is the rationale for not allowing cycles. Or that is how I
understood this issue when reading the spec. 

I think that this issue should be resolved by allow the RDFS subPropertyOf
and subClassOf stay the way they are, and then do the natural thing in
daml+oil: We've got subPropertyOf, which is like '<', then define
something like superPropertyOf, and let it behave like '>='. Then I can go
on using subPropertyOf the way I'm used to. And you could just change
subPropertyOf(X,Y) to superProperty(Y,X).

Yours,

Sigge

Received on Monday, 5 March 2001 09:32:53 UTC