Defining a term defining relations

Hi,
I got a question regarding semantics (maybe suitable for a different
mailing list? which?) - essentially my question is if term definition
relations can be separated from other relations, which would be in my
opinion useful information for deciding if a definition of a term has
changed - it would enable a semantic processor to know it understands a
term completely.
For example relations "is instance of" (rdf:type) concerning an OWL
class usually don't affect its semantics (unless it's a class defined by
enumeration of instances). Similar for comments in natural language and
other annotations.
I suppose this property of ontology language terms is defined in the OWL
and other respective specifications, but isn't there a value in terms to
define (possibly restrict) the semantics-defining nature of ontology
language terms across various ontology languages in machine readable way
(essentially a meta-ontology language)? Has this been already done?

Best,
Jiri Prochazka