COORDINATION OF DISTRIBUTED AND PARALLEL ACTIVITIES IN THE IWIM MODEL

We present an alternative way of designing new as well as using existi ng coordination models for parallel and distributed environments. This approach is based on a complete symmetry between and decoupling of pr oducers and consumers, as well as a dear distinction between the compu tation and the coordination/communication work performed by each proce ss. The novel ideas are: (i) to allow both producer and consumer proce sses 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 proc esses involved in a coordinated activity, and (ii) to introduce contro l or state driven changes (as opposed to the data-driven changes usual ly 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 fun ctionality of the proposed model can be realised in a general coordina tion framework, namely the Shared Dataspace one, using as driving forc e 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 t hat the proposed apparatus can be used for other Shared-Dataspace-like coordination formalisms with little modification.