In order to regulate different circumstances over an extensive period of time, norms in institutions are stated in a vague and biguous manner, thereby abstracting from concrete aspects, which are relevant for the operationalization of institutions. If agent-based electronic institutions, which adhere of abstract requirements, are to be built, how can those requirements be translated into more concrete constraints, the impact of which can be described directly in the institution? We address this issue considering institutions as normative systems based on articulate ontologies of the agent domain they regulate. Ontologies, we hold, are used by institutions to relate the abstract concepts in which their norms are formulated, to their concrete application domain. In this view, different institutions can implement the same set of norms in different ways as far as they presuppose divergent ontologies of the concepts in which that set of norms is formulated. In this paper we analyze this ph...