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Re: Multiple ontologies in a single file: RDF vs. the rest

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Mon, 19 May 2008 13:08:17 +0200
Cc: public-owl-wg@w3.org
Message-Id: <645CF2F3-7C7E-49C0-9504-7A70DC397CAA@uva.nl>
To: Peter F. Patel-Schneider <pfps@research.bell-labs.com>

On 7 mei 2008, at 13:32, Peter F. Patel-Schneider wrote:


> A way forward would be to require in the schema that an OWL 2 ontology
> document in XML form match against a single Ontology element.  The
> problem is that tools may want to validate bits of an ontology so  
> things
> like Axiom need to be top-level elements as well.  (Right now, an  
> OWL 2
> XML document could, I suppose, consist of a sequence of intermixed
> Ontology, Datatype, and ObjectUnionOf elements.)  Perhaps some XML
> Schema hacker could come up with the appropriate incantations to allow
> this.

XML Schema is designed exactly with (partial) validation by tools in  
mind. On the other hand, there may indeed be some way of enforcing a  
single root element if that is the only globally declared element. It  
will become a really ugly schema though.


> The way forward is, I think, to add wording to effect that RDF graphs
> that are the result of the forward mapping are expected to be stored  
> as
> single docments at the location suggested in the soon-to-be-determined
> section on publishing ontologies on the web.  I believe that the web
> retrieval mechanisms make it possible to store both an OWL 2  
> ontology in
> RDF/XML form and an OWL 2 ontology in XML form at the same web  
> location.

Yes, that's reasonable (provided that we have the proper mime types in  
place, I guess)

> I do not believe that the working group can be in the business of
> determining how triple stores work.  It is certainly a problem if  
> there
> is no way of locally storing OWL 2 ontologies in RDF graph form.
> However, I do not believe that this is the case.
> Triple stores that completely eliminate the source of triples  
> internally
> do have problems with many high-level organizations of triples.  I
> expect that there are very few, if any, of these sorts of triple
> stores.  Triple stores that do record the source of triples (quad
> stores) can support the discrimination required to reverse map OWL 2
> ontologies.

Ok. Hadn't really taken quad stores into account. Thanks for the  

> Of course, if the working group decides that it must be possible to
> extract OWL 2 ontologies from within a triple store that does not  
> record
> the source of triples, it is possible to do so by drastically changing
> the RDF mapping of OWL 2 ontologies.  I would probably not object to
> such a change, but I could not provide much help for the required
> changes to the OWL 2 Full semantics.

I wouldn't object either, but it might be a whole lot of overhead for  
little or no gain.


> We could, actually, allow multiple OWL 2 ontologies per document in  
> the
> functional syntax with a very small change.  I'm not suggesting we do
> this, primarily because of imports (although having all the versions  
> of
> an ontology in the same document is actually a semi-reasonable
> approach).  However, it makes things much easier if each document  
> has a
> single ontology in RDF, and reflecting this limitation of RDF in the
> other syntaxes makes life easier overall.

I agree it would be easier, but don't know whether it is desirable.

Got me thinking... we are currently excluding the possibility of  
having a single ontology spanning multiple files. Would there be use  
cases for that?

> (Answer: RDF/XML is the official RDF serialization syntax.  The
> N-triples and Turtle syntaxes for RDF graphs get used because they  
> have
> advantages over RDF/XML.  N-triples has a definition, but I do not
> believe that there is any official mechanism for storing or  
> transferring
> N-triples documents - Jeremy may know better.  Turtle is more  
> official,
> as there is a defining document and a MIME type for Turtle.   
> (However, I
> do not believe that there is any official word on how to translate
> Turtle into RDF graphs.)  N3 doesn't fit into the mix here, as it is  
> not
> a viable syntax for RDF graphs.)

Thanks again for the clarification!


>> -Rinke
> peter

Drs. Rinke Hoekstra

Email: hoekstra@uva.nl    Skype:  rinkehoekstra
Phone: +31-20-5253499     Fax:   +31-20-5253495
Web:   http://www.leibnizcenter.org/users/rinke

Leibniz Center for Law,          Faculty of Law
University of Amsterdam,            PO Box 1030
1000 BA  Amsterdam,             The Netherlands
Received on Monday, 19 May 2008 11:08:57 UTC

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