Law-governed interaction: A coordination and control mechanism for heterogeneous distributed systems

Software technology is undergoing a transition from monolithic systems, constructed according to a single overall design, into conglomerates of semiautonomous, heterogeneous, and independently designed subsystems, constructed and managed by different organizations, with little, if any, knowledge of each other. Among the problems inherent in such conglomerates, none is more serious than the difficulty to control the activities of the disparate agents operating in it, and the difficulty for such agents to coordinate their activities with each other. We argue that the nature of coordination and control required for such systems calls for the following principles to be satisfied: (1) coordination policies need to be enforced; (2) the enforcement needs to be decentralized; and (3) coordination policies need to be formulated explicitly-rather than being implicit in the code of the agents involved-and they should be enforced by means of a generic, broad spectrum mechanism; and (4) it should be possible to deploy and enforce a policy incrementally, without exacting any cost from agents and activities not subject to it. We describe a mechanism called law-governed interaction (LGI), currently implemented by the Moses toolkit, which has been designed to satisfy these principles. We show that LGI is at least as general as a conventional centralized coordination mechanism (CCM), and that it is more scalable, and generally more efficient, than CCM.