W3C home > Mailing lists > Public > public-webont-comments@w3.org > April 2003

Re: Some comments on OWL Reference

From: Guus Schreiber <schreiber@cs.vu.nl>
Date: Fri, 04 Apr 2003 11:00:40 +0100
Message-ID: <3E8D57C8.8070504@cs.vu.nl>
To: Yuzhong Qu <yzqu@seu.edu.cn>
CC: webont-comments <public-webont-comments@w3.org>

Dear Yuzhong,

Thanks very much for your comments. The Working Group will consider
these and will get back to you in due course.

Regards, Guus Schreiber

Yuzhong Qu wrote:
> 1. The PRECISE SYNTAX  of OWL
> 
> The OWL Reference says:
> [   1.1 Purpose of this document
>     ...
>     The normative reference on the *PRECISE SYNTAX* of the OWL language constructs can be found in the OWL Semantics and Abstract Syntax document.
>     ...
>     1.3 OWL syntax 
>     An OWL ontology is encoded and written as an RDF graph, which is in turn a set of RDF triples. As with any RDF graph, an OWL ontology graph can be written in many different syntactic forms (as described in the RDF/XML Syntax Specification (Revised) ...).
>     ...
>     1.7 Appendices to this document
>     Appendix B contains an RDF schema for the OWL language constructs. ....This schema provides the *BASIS* for the RDF/XML syntax of OWL. 
>     ...
> ]
> 
> The OWL S&AS says:
> [2. Abstract Syntax
>     (In the first paragraph.)
>     ....The syntax used here is rather *Informal*, ...
> ]
> 
> The OWL Overview says:
> [1.1 Document Roadmap
>     ...
>     The OWL Semantics and Abstract Syntax document is the *Final and Formally* stated normative definition of the language. 
> 
> ]
> 
> It seems to me that:
> 1) There is no PRECISE SYNTAX  of OWL. 
> 2) The XML encoding of an OWL ontology is based on RDF/XML Syntax as well as RDF schema for OWL (Appendix B).
> 3) Without the PRECISE SYNTAX of OWL, where does the *Final and Formally* stated normative definition of the language come from?
> 
> I think that the specs should give a consistent and explicit stating on this issue.
> 
> 
> 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.
> 
> 
> 3. RDF schema for OWL (Appendix B)
> 
> 1) "rdf:resource" is a typo error as I mentioned before. It should be "rdfs:Resource".
> 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?
> 
> 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 ?
> 
> 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).
> 
> 
> Yuzhong Qu
> Dept.Computer Science and Engineering
> Southest University, Nanjing, China
> http://cse.seu.edu.cn/People/yzqu/en
> 
> 
> 

-- 
A. Th. Schreiber
Free University Amsterdam, Computer Science
De Boelelaan 1018a, 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 Monday, 7 April 2003 12:59:15 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:43:27 GMT