Coordination for Component Composition

Composition of systems out of autonomous subsystems pivots on coordination concerns that center on interaction. Interaction has been studied as an inseparable concern in concurrency theory. Curiously, however, interaction has not been seriously considered as a first-class concept in constructive models of computation. The coordination language Reo provides a powerful and expressive model for flexible composition of behavior through interaction. Reo serves as a good example of a constructive model of computation that treats interaction as a (in fact, the only) first-class concept. It uniquely focuses on the compositional construction of connectors that enable and coordinate the interactions among the constituents in a concurrent system, without their knowledge. We show how Reo allows complex behavior in a system to emerge as a composition of primitive interactions.