  Our ongoing work aims at defining an ontology-centered approach for building
expertise models for the CommonKADS methodology. This approach (which we have
named "OntoKADS") is founded on a core problem-solving ontology which
distinguishes between two conceptualization levels: at an object level, a set
of concepts enable us to define classes of problem-solving situations, and at a
meta level, a set of meta-concepts represent modeling primitives. In this
article, our presentation of OntoKADS will focus on the core ontology and, in
particular, on roles - the primitive situated at the interface between domain
knowledge and reasoning, and whose ontological status is still much debated. We
first propose a coherent, global, ontological framework which enables us to
account for this primitive. We then show how this novel characterization of the
primitive allows definition of new rules for the construction of expertise
models.
