Combining event-and state-based norms

Institutions offer a mechanism to regulate the behaviour of agents without the need for these agents to internalise the norms of the system. Current formalisms can be divided in two groups depending on whether norms are expressed on the state of the normative structure or the events that bring about normative change. This paper argues that for complex systems both types are needed. To this extend, we introduce ESI, a formal model for institutions incorporating the concepts for both eventand state-based normative modelling. We demonstrate our approach with a simplified legal case-study.