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RE: DAML+OIL (March 2001) released

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 11 Apr 2001 14:38:50 -0400
To: lhart@grci.com
Cc: www-rdf-logic@w3.org
Message-Id: <20010411143850N.pfps@research.bell-labs.com>
From: "Hart, Lewis" <lhart@grci.com>
Subject: RE: DAML+OIL (March 2001) released
Date: Tue, 10 Apr 2001 11:11:28 -0400

> Some examples of questions I have are: 
> Consider this partial definition from the latest spec...
> <rdf:Property rdf:ID="unionOf">
>   ... omitted ...
>   <rdfs:domain rdf:resource="#Class"/>
>   <rdfs:range rdf:resource="#List"/>
> </rdf:Property>
> Why is it not defined like this:
> <ObjectProperty rdf:ID="unionOf">
>   ... omitted ...
>   <domain rdf:resource="#Class"/>
>   <range rdf:resource="#List"/>
> </ObjectProperty>

The main reason, in my mind, at least, would be that ObjectProperty should
be used for properties in a particular theory (or KB, or whatever you want
to call it).  unionOf is an interpreted property (for DAML+OIL), with a
specific meaning for DAML+OIL (i.e., it is part of the theory of DAML+OIL,
and thus part of the meta-theory).  I don't think that there is any
indication in the DAML+OIL documents that this distinction should be made,
but perhaps it should.

> Specifically, 
> 1. The semantics of rdfs:domain, which are "believed to be flawed" [1],  are
> different that the semantics of daml:domain. So, why is rdfs:domain used?
> Would it not, in general,  be preferred to use daml:domain in the DAML+OIL
> specification? 

We have gone back and forth on whether to use rdfs:domain or daml:domain,
or other, similar, equivalent names.  Right now, the rdfs and rdf versions
are used everywhere (I hope) and the equivalences are there only for users
who, perhaps, want to use fewer namespaces.

> 2. The property daml:unionOf is of type rdf:Property, but has domain and
> range of daml:Class and daml:List. How should a RDF (but not DAML) aware
> agent deal with that? Or, stated another way, if we are trying to allow some
> usability of DAML by RDF/RDFS only applications, this doesn't seem to
> support that.

daml:unionOf would not be usable (much) by non-DAML+OIL-aware
applications.  We have tried to retain as much overlap with RDF and RDFS as
possible, but, of course, any DAML+OIL construct that can not be embedded
into RDF or RDFS will not be (very) accessible from regular RDF and RDFS applications.

> 3. This is a property which relates objects to other objects, wouldn't the
> daml:unionOf be better defined as a daml:ObjectProperty?

See above.

> Thanks. - Lewis
> [1] http://www.daml.org/2001/03/reference.html#domain-def
> ___________________________________________
> Lewis L Hart 
> GRC International                           lhart@grci.com
> 1900 Gallows Rd.                  Voice (703)506-5938
> Vienna, Va 22182                    Fax (703)556-4261

Peter Patel-Schneider
Bell Labs Research

PS:  Thanks for the questions!
Received on Wednesday, 11 April 2001 14:40:14 UTC

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