Standardization experts in object modelling are having difficulties with defining the concept of role; for example, they are not sure of whether role is a type or an instance concept. This issue is a source of confusion in the UML standard, and prevents ISO experts to reach consensus and finalize a language for ODP enterprise modelling. In this paper, we make an in-depth analysis of the problem, find its likely causes, and come up with a proposal for a new ODP definition of role, as well as with definitions of related concepts. We expect our definitions and our results not only to achieve consensus among ISO delegates, but also to be a basis for improving the UML standard and related software engineering processes.