Reasoning About Norms, Obligations, Time and Agents

Reasoning about norms and time is of central concern to the regulation or control of the behavior of a multiagent system. In this paper we introduce a representation of normative systems that distinguishes between norms and the detached obligations of agents over time, leading to a simple and therefore practical way to reason about norms, obligations, time and agents. We consider the reasoning tasks to determine whether a norm is redundant in a normative system and whether two normative systems are equivalent. In the former case the redundant norm might be removed. In the latter case one norm might be replaced by the other. It is well known that properties concerning iterated or deontic detachment no longer hold when reasoning with multiple agents or with obligations over time. Yet, earlier approaches to reasoning about norms rarely consider the intricacies of time. We show how norms can be used to define the persistence of obligations of agents over time. We illustrate our approach by discussing three ways to relate norms and obligations of agents over time. Also we show how these three ways can be characterized.