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Re: Some comments on OWL Reference

From: Guus Schreiber <schreiber@cs.vu.nl>
Date: Fri, 25 Apr 2003 12:24:44 +0200
Message-ID: <3EA90CEC.40602@cs.vu.nl>
To: Yuzhong Qu <yzqu@seu.edu.cn>
CC: webont-comments <public-webont-comments@w3.org>

Yuzhong Qu commented:



This comment was answered by Jeremy Carrol:

 >  2. The domain and range of owl:equivalentClass in OWL Lite.
 >  [    3.2.2 owl:equivalentClass
 >      ...
 >      NOTE: OWL DL does not put any constraints on the types of class
 >      descriptions that can be used as domain and range values of an
 >      owl:equivalentClass statement. In OWL Lite **only class 
identifiers and
 >      property restrictions** are allowed as domain and range values. (?)
 >      8.3 OWL Lite
 >      ...
 >      the subject of owl:equivalentClass triples be named classes and
 >      the object of owl:equivalentClass triples be named classes,
 >      restrictions, or subjects of owl:intersectionOf triples (?);
 >      ...
 >  ]
 >  1) According to S&AS, the domain of owl:equivalentClass must be just
 >     classID.
 >  2) As to the range of owl:equivalentClass, class identifiers and
 >     property restrictions are certainly allowed as range values. But how
 >     about others allowed as range values? What's "the subjects of
 >     owl:intersectionOf triples" mentioned in section 8.3?
 >  It seems most likely to be anonymous classes defined as the
 >  conjunctions of class identifiers and property restrictions.
 >  It (The domain and range of owl:equivalentClass in OWL Lite) should
 >  be explicitly and consistently specified.

In OWL Lite the domain of owl:equivalentClass must be a named class
and the range must be be either a named class or a restriction..

We will delete the phrase "or subjects of owl:intersectionOf
triples" from the first bullet of the list in Sec. 8.3 of Reference.

 >  3. RDF schema for OWL (Appendix B)
 >  1) "rdf:resource" is a typo error as I mentioned before. It should be
 >     "rdfs:Resource".

"rdf:resource is written with a lowercase in constructions like:

<rdf:Property rdf:ID="backwardCompatibleWith">
    <rdfs:domain rdf:resource="#Ontology"/>
    <rdfs:range rdf:resource="#Ontology"/>

It is in the RDF namespace, so it should really be "rdf:"

 >  2) The definition of owl:Thing and owl:Nothing
 >  <Class rdf:ID="Thing">
 >    <rdfs:label>Thing</rdfs:label>
 >      <unionOf rdf:parseType="Collection">
 >       <Class rdf:about="#Nothing"/>
 >       <Class>
 >         <complementOf rdf:resource="#Nothing"/>
 >       </Class>
 >     </unionOf>
 >   </Class>
 >  <Class rdf:ID="Nothing">
 >    <rdfs:label>Nothing</rdfs:label>
 >    <complementOf rdf:resource="#Thing"/>
 >  </Class>
 >  I suggest the axiom for owl:Thing be simplified as follows:
 >   <Class rdf:ID="Thing">
 >    <rdfs:label>Thing</rdfs:label>
 >  </Class>
 >  Is there any lose of meaning?

We think so. The class axiom for owl:Thing defines its class extension
to be the extension of owl:Nothing plus its complement, which means all
individuals in the universe of discourse. owl:Nothing is its complement,
so its class extension is the empty set.

 >  I note owl:Nothing is not included in OWL Lite. [A note in section
 >  3.1 Class descriptions].
 >  Including owl:Nothing in OWL Lite will bring any harmness to OWL Lite ?

This comment will be answered in the context of your comments on OWL
S&AS, see Peter Patel-Schneider's message:

 >  4. The rdfs:range of owl:imports
 >  In Appendix C (OWL Quick Reference), the rdfs:range of owl:imports is
 >  missing. It should be owl:Ontology (according to Appendix B).

Thanks for spotting this. We will make the appropriate editorial change
to Appendix C.

 >  Yuzhong Qu

Please can you reply to this message on the public-webont-comments@w3.org
list, indicating whether we should be giving further consideration to your
comment or whether these pointers have adequately clarified the situation.

Thanks again very much for your comments.

Regards, Guus Schreiber

NOTE: new affiliation per April 1, 2003

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/ [under construction]
Received on Friday, 25 April 2003 06:24:51 UTC

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