Re: [Fwd: Rules for restrictions](same..As, equivalentTo)

From: Dan Connolly (
Date: 01/04/01

Tim Berners-Lee wrote:
> My questions about the DAML+OIL spec as revised may be based on ignorance of
> meetings I wasn't at, in which case I apologize - please accept them as
> clarification questions.

> 2. sameClassAs and equivalentTo; same comment as 1except for domain and
> range constraints.

This needs to be written up as a case-study in evolution... lemme
sketch it out:

An RDFS agent knows these two rules:

        :s :specl :o.
        :specl rdfs:subPropertyOf :genl.
         } log:implies {

        :s :genl :o.

        :x rdf:type :sub.
        :sub rdfs:subClassOf :super.
         } log:implies {

        :x rdf:type :super.

but it doesn't know anything about daml:equivalentTo.

and daml+ont.daml says

        daml:sameClassAs rdfs:subPropertyOf rdfs:subClassOf.

Thus, when an RDFS(-only) agent is presented with

        :Dog daml:sameClassAs :Canine.
        :sparky rdf:type :Dog.

it can conclude

        :Dog rdfs:subClassOf :Canine.
and hence
        :sparky rdf:type :Canine.

Unfortunately, in order to get and RDFS-only agent to infer

        :lassie rdf:type :Dog.


        :lassie rdf:type :Canine.

it must also be told

        :Canine daml:sameClassAs :Dog.

which is redundant for DAML agents.


>  Are we suggesting
> that ontology builders in turn should define "sameCarAs" and "sameVehicleAs"
> properties?

No, I don't think so; There's no W3C recommendation regarding
cars that we feel obliged to support.

> This is the example being set. I found that when converting
> between different syntaxes, one has to introduce daml:equivalentTo  as part
> of that translation, because different syntaxes have different abilties to
> map a graph into a tree. I missed it being defined by rdfs and now I see it
> has slipped out of daml.

er... huh? I'm not aware of any decision to get rid of

It's there:

        <Property ID="equivalentTo">

        $Id: daml+oil.daml,v 1.2 2001/01/02 19:15:55 mdean Exp $


        <equivalentTo,?C,?D>  IC(?C) = IC(?D)

        Wed, 03 Jan 2001 18:45:23 GMT
        $Revision: 1.2 $ of $Date: 2001/01/02 18:56:02 $

Hmm.. it's not used in
nor mentioned in

and I don't see it in "Appendix One: List of all language elements"
$Revision: 1.1 $ of $Date: 2001/01/03 18:38:43 $ 

So yes, it does seem to be slipping out. Frank, please document
it in the reference; i.e. in anything that claims
to be exhaustive; and if you get a chance, in the walkthru.

Dan Connolly, W3C

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