RE: URIs

Alan,

> Dereference, in that context, means something different than 
> what I was using the term for.
> They mean that there has to be a definition of the subject 
> and object in the OWL file or one of the imports.
> 
> I was using it to mean, go to the network and do a geturl of 
> the uri and do something with the results. OWL and RDF 
> doesn't specify that you do that. That would certainly not 
> work, since most of the URLs prior to the semantic web don't 
> have RDF or OWL content.

OWL/RDF is build on URI not vice versa.  If the dereference of a URI returns
a document that is not an RDF document, it simply means that the RDF engine
should stop dereferencing at that particular branch.

But I do agree, the processing model of the RDF is ambiguious.  There is no
explicit statement about if and when a URI should be dereferenced from an
RDF model.  For example, given a simple model of:

http://www.example.com/foo a http://www.example.com/bar.  

It is not clear if we should de-reference either URI.  Although OWL defines
an owl:import, I am still not sure about two problems:

First, it is still unclear how to process the URI in basic RDF document that
does not use OWL.
Second, owl:import must be used in an ontology header and its range must be
an owl:Ontology as well.

Then, my question is what is definition an Ontology?  For example, should
the above example case be an ontology?  
If not, then I cannot use any other ontologies in the sense of using
owl:import.  
If yes, what RDF/OWL statements are not ontology?

Two things needs to be clarified, IMHO.
(1) The default processing model of RDF.
(2) The owl:import should be changed.  Its namespace should be moved to
rdf/rdfs.  and its domain and range should be changed to "namespace" URI
rather than an "owl:ontology".

A related issue is whether the defined ontology/RDF statements should be
placed under its namespace URI. I firmly think it MUST but currently it is
not enforced by any standard. The matter is considered only as a best
practice issue.  But if an ontology is not placed under its namespace, I am
not sure how it can be used.  For instance, gene ontology is not placed
under its namespace.  Dereference its namesapce
http://www.geneontology.org/owl/# returns a 404. So, how you can use GO
under a generic RDF engine without specific tailored code?  

I have this confusion when thought about writing a clear definition of
ontology for the ontology task force, but cannot get a clear answer of
myself.  I am hoping that I can find more time to do more research on that.
But I might have overlooked something.  If everyone thinks not, maybe we
should raise the issue to the TAG group.

Xiaoshu

Received on Monday, 19 June 2006 15:25:29 UTC