Re: range, domain: Conjunctive AND disjunctive semantics both supportable

In the OIL language (see http://www.ontoknowledge.org/oil/) we extend
RDF schema with (amongst other things) logical constructs that allow
you to say things like:

	P --[rdfs:range]-> (A or B)

This approach has many advantages: it allows disjunctive semantics to
be exactly captured and it saves cluttering up the class hierarchy with
unwanted classes. Of course the meaning would only be accessible to
OIL-aware agents.

In this setting, given 

	S --P--> O

we can infer

	O --rdf:type--> (A or B)

Note that this is NOT the same as being able to infer either

	(O --rdf:type--> A)
or 
	(O --rdf:type--> B)

As for validity checking, without being able to express e.g., negation
or disjointness, then "validation" is not very meaningful as we can
never infer invalidity - we can only infer tighter constraints.

Regards, Ian