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Can DAML class also be an instance?

From: Stephen Reed <reed@cyc.com>
Date: Wed, 27 Jun 2001 10:33:13 -0500 (CDT)
To: www-rdf-logic@w3.org
Message-ID: <Pine.LNX.4.21.0106271024160.895-100000@balrog.cyc.com>
In the Cyc ontology we allow classes to be instances of other classes
which are meant to be types of classes.

An example is:

    <daml:Class rdf:ID="Doorway">
        <rdfs:comment>A collection of portals.  Each element of
            #$Doorway is a portal in some instance of
            #$ShelterConstruction, suitable for people (and perhaps
            vehicles) to enter and exit.  For example, doorways to
            houses, office buildings, elevators, automobiles, airplanes,
            garages, etc.</rdfs:comment>
        <rdf:type rdf:resource="#ExistingObjectType"/>
        <rdfs:subClassOf rdf:resource="#Portal"/>
        <rdfs:subClassOf rdf:resource="#Artifact"/>

Doorways are subclasses of Portals and Artifacts, and the class of
doorways is an instance of the class of types of existing objects.

Is it legal DAML+OIL to have both type and subClassOf statements
describing a class? 

I presently fail the DAML XML validator on this point.

Stephen L. Reed                  phone:  512.342.4036
Cycorp, Suite 100                  fax:  512.342.4040
3721 Executive Center Drive      email:  reed@cyc.com
Austin, TX 78731                   web:  http://www.cyc.com
Received on Wednesday, 27 June 2001 11:33:16 UTC

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