From: Jim Hendler (jhendler@darpa.mil)
Date: 07/09/01
At 11:17 AM +0100 7/9/01, Ian Horrocks wrote:
>Dan,
>
>On July 7, Dan Brickley writes:
> >
> > Hi
> >
> > (I'm unlurking; as RDF Core WG work on RDF Schema is starting up, I'm
> > hoping to have more time to spend on DAML+OIL stuff too)
> >
> > So I'm looking at some of the DAML+OIL definitions, while preparing a
> > new draft of RDF Schema for the RDF Core WG. Reviewing the equivalentTo /
> > sameClassAs machinery:
> >
> > DAML+OIL says... (larger excerpt coped below)
> >
> > for equivalentTo(X, Y), read X is an equivalent term to Y.
> > and
> > for sameClassAs(X, Y), read X is an equivalent class to Y.
> > cf OIL Equivalent
> >
I think I'm a lot to "blame" on this one - we spent a long time on
the issue, and finally decided we wanted both. From an "ontologist"
point of view, it makes sense to use the various "same..."
constructs, because you know what is a class, a property, or an
individual. However, from a user/implementor point of view, some of
us felt that it was important to be able to state an equivalence even
if one didn't know what something was. For example, if I want to say
in some B2B application that what Frank calls a "product-number" is
the same thing that Dan call a "Product-code" -- I can assert
Frank:product-number daml:equivalentTo Dan:Product-code;
without knowing whether it is a property or a class (or even an
individual if I was saying mailto:danbri daml:equivalentTo
http://www... which is semantically odd, but quite powerful for
rule-based inferencing if I'm merging different sets of information
about people).
So the note that these look like different approaches shows that Dan
has caught the essence of the issue - we do have (and maybe need)
these differences
-JH
Dr. James Hendler jhendler@darpa.mil
Chief Scientist, DARPA/ISO 703-696-2238 (phone)
3701 N. Fairfax Dr. 703-696-2201 (Fax)
Arlington, VA 22203 http://www.cs.umd.edu/~hendler
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