A Formal Model of Responsibilities in Agent-Based Teamwork

Responsibilities are an important component of teamwork in multi-agent systems. In this paper, we present a formal model of responsibilities based on beliefs and goals. Our approach focuses on two central features of responsibilities: persistence and dependency. We define a special form of persistence that obligates agents to keep trying an action until it is done, but allows the caveat that they might delegate the task. Dependency means that the responsibility was assigned by a delegating agent who wants it done. We model this dependency through a requirement to maintain mutual belief on the status of the goal, as well as the need by the superior, and the achievability by the subordinate. Thus agents with responsibilities are guaranteed to inform their superiors when they are about to fail, allowing others to take over, which provides robustness. Finally, we treat joint responsibilities among multiple agents as a mutual agreement to keep each other informed of their individual abilities to achieve the goal. These definitions provide a semantics for responsibilities in multi-agent systems, and can be used to design correct specifications of agent behavior, and justify decisions such as when to act, wait, or communicate within a team.