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Re: Proposed response to: e: Restriction, DeprecatedClass in OWL Language Reference 31 March 2003

From: Jim Hendler <hendler@cs.umd.edu>
Date: Tue, 24 Jun 2003 10:12:44 -0400
Message-Id: <p05200f0cbb1e0c70d353@[]>
To: Guus Schreiber <schreiber@cs.vu.nl>, WebOnt WG <www-webont-wg@w3.org>

Guus - the only change I would make is to change the penulatimate 
paragraph to something in like:

The WG does not see the rationale for introducing owl:Entity at this 
time. I would suggest the discussion of this issue at the 
rdf-logic@w3.org discussion list.

then SEND IT!

At 2:24 PM +0200 6/24/03, Guus Schreiber wrote:
>Richard H. McCullough wrote:
>>  From: "Richard H. McCullough" <rhm@cdepot.net>
>>  Subject: Re: Restriction, DeprecatedClass  in OWL Language 
>>Reference 31 March 2003
>>  So your class hierarchy is
>>      rdfs:Class
>>          owl:Class
>>          owl:Restriction
>>          owl:DeprecatedClass
>Sorry if the previous message was not clear enough. The class 
>hierarchy is (see Appendix B of Reference)
>     owl:Class
>         owl:Restriction
>     owl:DeprecatedClass
>So, owl:Restriction is a specific kind of owl:Class.
>>  That raises several questions in my mind.
>>  1. Shouldn't you strive for
>>      owl:Class  owl:sameAs  rdfs:Class
>This is true in a weaker sense in OWL Full (owl:Class 
>owl:equivalentClass rdfs:Class), but not in OWL DL. See the note in 
>Sec. 3.1 in the editor's draft of OWL Reference [1]:
>NOTE: owl:Class is defined as a subclass of rdfs:Class. The 
>rationale for having a separate OWL class construct lies in the 
>restrictions on OWL DL (and thus also on OWL Lite), which imply that 
>not all RDFS classes are legal OWL DL classes. In OWL Full these 
>restrictions do not exist and therefore owl:Class and rdfs:Class are 
>equivalent in OWL Full.
>>  2. Shouldn't owl:Restriction be a metaclass of rdf:Property?
>>      owl:Restriction  rdfs:subClassOf  rdf:Property
>owl:Restriction is not a property, it is a class description of 
>which the class extension is defined in terms of property 
>constraints. See Sec. 3.1.2:
>The class owl:Restriction is defined as a subclass of owl:Class. A 
>restriction class should have exactly one triple linking the 
>restriction to a particular property, using the  owl:onProperty 
>property. The restriction class should also have exactly one triple 
>that represents the value constraint c.q. cardinality constraint on 
>the property under consideration, e.g., that the cardinality of the 
>property is exactly 1.
>>  3. Likewise, shouldn't these be subClasses of rdf:Property
>>       owl:DataRange
>This is not a property, but a class that can act as a datatype. See Sec. 6.2:
>In the case of an enumerated datatype, the domain value of owl:oneOf 
>is a blank node of class owl:DataRange ....
>>       rdfs:Datatyp
>>       rdfs:Literal
>This is outside the scope of the OWL specifications. I would think 
>this is not the case, however.
>>       owl:DeprecatedProperty
>Correct, see Appendix B:
><rdfs:Class rdf:ID="DeprecatedProperty">
>   <rdfs:label>DeprecatedProperty</rdfs:label>
>   <rdfs:subClassOf rdf:resource="&rdf;Property"/>
>>  4. It would be desirable to define an owl:Entity class,
>>  disjoint from rdf:Property, which would include as subClasses
>>      owl:AllDifferent
>>      rdfs:Container
>>      owl:DeprecatedClass
>>      owl:Enumeration
>>      owl:Intersection
>>      rdf:List
>>      owl:Ontology
>>      owl:Union
>>  5. The above would produce the Class hierarchy
>>      owl:Thing
>>          owl:Entity
>>          rdf:Property
>>          rdf:Statement
>>  where Entity,Property,Statement are disjoint and exhaustive.
>>  This hierarchy is very meaningful, from both  metaphysical
>>  and epistemological viewpoints.
>>  Entity is the class of primary things that exist.
>>  Property is the class of Entity properties plus meta properties
>>      (properties of things other than entities).
>>  Statement is the class of relations between things.
>I;m not completely sure about the rationale for introducing 
>owl:Entity. I would suggest to discuss this issue at the 
>rdf-logic@w3.org discussion list.
>Thanks for your comments. Please let us know whether this response 
>is satisfactory.
>Guus Schreiber
>>  Dick McCullough
>>  knowledge := man do identify od existent done;
>>  knowledge haspart proposition list;
>Free University Amsterdam, Computer Science
>De Boelelaan 1081a, 1081 HV Amsterdam, The Netherlands
>Tel: +31 20 444 7739/7718
>E-mail: schreiber@cs.vu.nl
>Home page: http://www.cs.vu.nl/~guus/

Professor James Hendler				  hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies	  301-405-2696
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Received on Tuesday, 24 June 2003 10:12:50 UTC

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