[This is a response to a number of other messages in this thread]
On 2007 Sep 28, at 08:20, Andrea Preite Martinez wrote:
> On the other hand, I think that the discussion of vocabularies AND
> ontologies, of SKOS or OWL, is perfectly irrelevant to the present
> user requirements.
The problem with 'SKOS or OWL' is that a vocabulary isn't an ontology. Adding "<> a owl:Ontology", and changing skos:Concept to owl:Class doesn't make it one.
The super-/sub-class relations in an ontology are required to be homogeneous, in that all instances of a subclass are necessarily also instances of the superclass, and that simply doesn't work for the 'kinematics' NT 'acceleration' example I mentioned earlier. Avoiding expressing those, and just adding a lot of SKOS terms produces a strange mutant: a SKOS vocabulary which has a few OWL terms in it, adding some syntactical baggage without (as far as I can see) doing a lot of work.
[The next three paras are formal minutiae]
There's also a technical difference, which is that the things which are of type skos:Concept are specifically 'concepts', not other things. Thus an OWL class myns1:Star is (probably) the class of things which are stars; a skos:Concept myns2:Star is an _instance_ which names 'the concept of a star'. The skos:Concept myns2:VariableStar is not a subclass of myns2:Star, because neither of them is a class. This sounds nit-picky, but is the suggestion that we'd get ourselves in trouble one way or another -- we'd end up saying something nonsensical and deduce rubbish -- if we conflate the two.
There's an example at the end of the SKOS spec which distinguishes the dc:creator of the concept of "Henry VIII" (which might be me, today), from the dc:creator of "Henry VIII" (the person/instance, which was done by "Henry VII" and "Elizabeth of York"), and neither of those things is the class of things which are Henry VIII (now get an aspirin).
OK, so talk about the owl:Class myns1:Star and develop that in parallel with the skos:Concept myns2:Star, perhaps linking them with something like myns1:hasAssociatedConcept. But then you're developing a vocabulary and an ontology both at once, and it's not clear (to me) what work the ontology half is doing.
Short version: I don't see the Requirement for an ontology.
All the best
Norman
-- ------------------------------------------------------------ Norman Gray : http://nxg.me.uk eurovotech.org : University of Leicester, UKReceived on 2007-09-30Z16:58:45