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Re: Review of Reference

From: Jim Hendler <hendler@cs.umd.edu>
Date: Thu, 2 Jan 2003 18:58:37 -0500
Message-Id: <p05200f74ba3a713b7bc8@[]>
To: Jeff Heflin <heflin@cse.lehigh.edu>, WebOnt <www-webont-wg@w3.org>

>- Language structure, para. 3, "An OWL ontology consists of an optional
>ontology element.": The element shouldn't be optional. If the person
>want their document to be an ontology, it should have an ontology
>element. Of course, they are free to define classes and properties in
>other documents, and they may not define any classes and properties in a
>document with owl:Ontology, but neither of these should be encouraged.

encouraging the use of owl:ontology is okay by me,  Requiring it did 
not receive consensus in the WG, and thus the reference should not 
make it required.

>- Class elements, sameAs bullet: owl:sameAs when applied to a class DOES
>NOT have the same semantics as owl:sameClassAs. owl:sameAs is a synonym
>for sameIndividualAs which when applied to classes say they are the same
>individuals and thus have the same properties, including e.g. the same
>values for rdfs:label. owl:sameClassAs only means that the two classes
>have the same extension (i.e., the same members) and says nothing about
>what properties the two classes have in common.

we need to get this right.  I can live either way - but we have made 
Semantics the normative for this, and it agrees with what Jeff says 
above (as I understand it) so Ref should be changed.

>- Property elements, last para. "A property is a binary relation that
>may or may not be defined in the ontology." Did the WG ever discuss
>whether or not it was legal to reference a class or property that wasn't
>defined in the ontology? I certainly would not support this. It makes it
>even easier for errors to creep into ontologies.

I must be missing something, we had long discussion about reference 
to things outside current ontology during the imports debate in 
particular.  I can certainly say in document A that something is a 
B:foo (foo a class) where B is a different document and no imports is 
specified.  Do you mean something different by "not defined in the 

>- The RDF Schema for OWL should be textually included in the document,
>so that if people print it out, they get it as well

great idea

>Here are some additional comemnts on
>- We should import the Dublin Core schema. i.e. add:
>   <imports rdf:resource="http://purl.org/dc/elements/1.1/">
>to the ontology header.

I endorse this idea - consistent with previous decisions re: Dublin 
Core, and makes it easier to use DC in OWL.

Professor James Hendler				  hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies	  301-405-2696
Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)
Received on Thursday, 2 January 2003 18:58:42 UTC

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