Re: definition of domain

Jeen Broekstra wrote:

> > What I find a bit unfortunate is the fact that a defined
> > property may only be used on instances of the class mentioned
> > in the domain. I believe the property should also be applicable
> > for aubclasses of the class in the domain.
> It is. In the definition of subClassOf it states:
>     2.3.2. rdfs:subClassOf
>     This property specifies a subset/superset relation between
>     classes. The rdfs:subClassOf property is transitive. If class
>     [snip]

I clearly phrased my thoughts the wrong way. See answer to Pierre-Antoine. With applying the
property to a subclass, I really mean the sublcass (node in a drawing) itself and not the
subclass'es instances.

> I have added the RDF descriptions of your examples below, with
> some comments.
> > E.g. suppose the following is defined:
> >  *  class 'animal'
>     <rdfs:Class ID="animal"/>
> >  *  property 'eats' with domain animal
>     <rdf:Property ID="eats">
>         <rdfs:domain rdf:resource="#animal"/>
>     </rdf:Property>
> > I would like to introduce now the class 'carnivore' as subclass of animal
> > with the restriction that 'carnivore' only eats 'animal'.
> This is not possible in RDFS. You can not restrict domain/range
> of a property locally (= in a class definition).

This is exactly what my question is all about: why should this not be possible? Why has W3C put such
restricitons on the use of 'domain'? Do they have thorough reasons to define 'domain' in this way or
did they just not see the use of applying properties not only to class instances, but also in the
definitions of subclasses (if you draw this, you see that you apply the property then to the
sublcass, hence my confusing terminology). I think W3C should change the semantics behind 'domain'
in the RDFS spec, unless they have good design issues for the current semantics.
It would be inefficient to push people to unintuitive modelling just because of some arbitrary
definition in a spec. Sometimes we have to question the bible! Amen.

By the way Jeen, I have to admit that your inferencing capabilities outrun mine. I can only argue
that the example was ment to give an intuitive feeling of the direction I would like to go.



Received on Thursday, 12 October 2000 06:55:17 UTC