Design of Autonomous, Distributed Systems

The paper describes an approach to organizing a collection of spatially distributed entities into a system capable of carrying out different complex missions. The entities are devices (artifacts like vehicles, sensors, actuators, computing and communications equipment) or agents or controllers, which control devices or other agents. The systemlevel capabilities concern complicated activities such as reconnaissance and logistics, requiring optimization, planning, and real-time control. The approach is to construct a system-level capability by appropriately organizing (composing) agents that can execute a small set of tasks. Agents are organized in a hierarchy: those at upper layers have authority over those at lower layers. The capability to conduct different missions is achieved by changing the agent architecture. The hybrid system specification and simulation language SHIFT is convenient for describing devices and agents, and their interaction. The paper gives two illustrative designs, one specified in SHIFT. To deploy systems organized in this way poses several research challenges, one of which is indicated here—the need for an exception-handling facility that provides a ‘fallback’ mechanism if an agent is unable to complete the task assigned to it.