Coordination of Distributed and Parallel Activities in the IWIM Model

We present an alternative way of designing new as well as using existing coordination models for parallel and distributed environments. This approach is based on a complete symmetry between and decoupling of producers and consumers, as well as a clear distinction between the computation and the coordination/ communication work performed by each process. The novel ideas are: (i) to allow both producer and consumer processes to communicate with each other in a fashion that does not dictate any one of them to have specific knowledge about the rest of the processes involved in a coordinated activity, and (ii) to introduce control or state driven changes (as opposed to the data-driven changes usually employed) to the current state of a computation. Although a direct realisation of this model in terms of a concrete coordination language does exist, we argue that the underlying principles can be applied to other similar models. We demonstrate our point by showing how the functionality of the proposed model can be realised in a general coordination framework, namely the Shared Dataspace one, using as driving force the Linda-based formalism. Our demonstration achieves the following objectives: (i) yields an alternative (control- rather than data-driven) Linda-based coordination framework, and (ii) does it in such a way that the proposed apparatus can be used for other Shared-Dataspace-like coordination formalisms with little modification.