Re: extend an Ontology

On Sat, 13 Oct 2001, Wolfgang Nejdl wrote:

> > [1  <text/plain; iso-8859-1 (8bit)>]
> > I think I did not express my self clearly… or else I did not fully
> > understand the reply
> >
> > What I had in mind is, in an existing ontology one of the ObjectProperties
> > is applicable over a certain range… Would it be possible to use the same
> > property but use a different range..In this case the range is another class?
> >
>
> No, you can only restrict the range of the property, not change it
> completely to another range (in DAML+OIL; in RDFS you can't even do
> that, because only one range is allowed per property)

We're fixing that; watch this space. See decisions of RDF Core WG f2f,
http://www.w3.org/2001/sw/RDFCore/20010801-f2f/
	[
	Multiple domain and range constraints are permissable and will have
	conjunctive semantics and this issue is now closed.
	]


You can kinda change to a different range, eg. from a different ontology
with a different way of categorising the world, so long as the specific
individuals that the property is used to point to happen to be members of
each of the range classes.

Consider for eg a property eg util:teacher that might be declared to have
a range of edu:Educator. Someone else might come along and say it also has
a range of wordnet:Person. Now, there might be instances of edu:Educator
in existence that are not members of wordnet:Person (robots!), and there
may be members of wordnet:Person who are not educators. We don't need
there to be a simple hierarchy where one class includes the other; often
ontologies will carve the world up differently. What we do
require though in this two-ranges example is that anything that is the
value of the util:teacher property of some resource be both an
edu:Educator _and_ a wordnet:Person.

Dan

Received on Saturday, 13 October 2001 12:06:45 UTC