Coordination Models Based on a Formal Model of Distributed Object Reflection

We propose a family of models of coordination of distributed object systems representing different views, with refinement relations between the different views. We start with distributed objects interacting via asynchronous message passing. The semantics of such a system is a set of event partial orders (event diagrams) giving the interactions during possible system executions. A global coordination requirement is a constraint on the allowed event diagrams. A system coordination specification consists of a meta-level coordinator that controls message delivery in the system according to a given global policy. The systemwide coordination can be refined/distributed using coordinators for disjoint subsystems that communicate with their peers to enforce the global policy. By a further transformation the meta-level can be replaced by systematically transformed base-level objects communicating via a controller object. The coordination models are formalized in rewriting logic using the Reflective Russian Dolls model of distributed object reflection. The general ideas are illustrated with several examples.