Re: comment: WD 10 May 2005

Hi John,

First I want to say that I agree with Bernard's explanation of this. 
Developing SKOS is about _re-using_ valuable 
thesauri/terminologies/... as they are (providing a standard RDF/OWL 
model for them) and as they have been developed for over many years in 
their communities, instead of trying to re-engineer them into ontologies.

> resources by the terms defined within an ontology. Under SKOS, the whole
> ontology seems duplicated so that each resource's <dc:Subject> value can

Which ontology? There is no ontology.

> CONCEPT DEFINITION. What is "a term in a controlled vocabulary" (your words) if
> not an rdfs:Class -- this is not asked rhetorically at all. Perhaps your

I think the point here is that the "hierarchies" that are present in 
e.g. thesauri are not subclass hierarchies. If we would like to 
convert from their original format (e.g. text, XML, DB) to RDF/OWL, 
then turning each node into an instance of rdfs:Class won't result in 
a valid class hierarchy. Then it seems better to stick to the original 
(much weaker) broader/narrower concept/term/node/... structuring of 
the hierarchy and simply recast it into RDF/OWL as 
skos:broader/narrower skos:Concept. Then applications using it can 
choose how to interpret the relationships (as it always has been I 
guess, only now we can also use the thesaurus on the SW).

> My alternative view is that a 'concept' is a document-related class of resources
> distinguishable by a Reasoner from the classes of terms defined within an
> ontology being used by or specified within the document. Resources can be
> categorized as being 'of' a concept either by a property, eg <dc:Subject>, or by
> an <rdf:type> element which specifies the Concept instance. Conversely, the

Because the skos:Concepts shouldn't be interpreted as being classes I 
think the rdf:type is not how a skos:Concept should be used in 
indexing a document. BTW if it were, then how would we distinguish 
between instances of a class/skos:Concept Person in the "normal sense" 
(i.e. instances of real people) and documents that have an rdf:type 
relation to this same class/skos:Concept Person?


> TOPIC RELATION. I see no conceptual semantic difference, and little has been
> offered, between a concept and a topic. My view is that every concept IS a

I think they might be the same. Is this referring to Topic Maps? I'm 
not sure what you are suggesting here if your conclusion holds.

> Lastly, and perhaps this is better left for later, I see little difference
> between a 'category' and a concept, topic, or class -- in my own ontology I use
> the metaclass 'Category' because it seems more user-friendly. Its Word Net

I think there is definately a difference between category, concept, 
topic on the one hand and class on the other, basically because 
rdfs:Class has a formal meaning while the others e.g. skos:Concept is 
not that strict. That is actually the reason for having skos:Concept 
at all.

> Concept. For instance, while the 'broader' property appears directly equivalent
> to rdfs:subClassOf, the 'narrower' property is not formally accommodated. Child

I think this is explicitly *not* the case.

> I haven't time now to analyze other SKOS properties... Bottom-line, the SKOS
> data model remains ambiguous to me so I would much appreciate it if SKOS could
> make a rigorous distinction between a class, topic, concept, subject, and
> category -- to help practitioners like myself understand best practices on the
> Semantic Web.

Although the Guide [1] does refer to the necessary terminology (e.g. 
the Willpower glossary [2]) to understand the Guide, it indeed seems 
to create a lot of confusion, so it seems like a good idea to make 
this more clear in the Introduction of the Guide. It already contains 
an example from the UKAT thesaurus which violates normal subclass 
modeling: Economic policy is not a superclass of Economic cooperation. 
Would such an explanation make it easier to read?

Best regards,
Mark van Assem.

-- 

[1] http://www.w3.org/TR/2005/WD-swbp-skos-core-guide-20050510/
[2] http://www.willpowerinfo.co.uk/glossary.htm

-- 
  Mark F.J. van Assem - Vrije Universiteit Amsterdam
        mark@cs.vu.nl - http://www.cs.vu.nl/~mark

Received on Thursday, 21 July 2005 09:37:38 UTC