Re: equivalentTo / sameClassAs / sameIndividualAs puzzle

From: Jim Hendler (
Date: 07/09/01

At 11:17 AM +0100 7/9/01, Ian Horrocks wrote:
>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


Dr. James Hendler
Chief Scientist, DARPA/ISO	703-696-2238 (phone)
3701 N. Fairfax Dr.		703-696-2201 (Fax)
Arlington, VA 22203

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