A distributed coordinated atomic action scheme

Coordinated Atomic actions have proved to be a very general concept which can be successfully applied for structuring complex concurrent systems consisting of elements which both cooperate and compete. The canonical Coordinated Atomic action is built of several cooperating participants (roles) and a set of local objects which represent the action state and provide the feature for cooperation. In addition, Coordinated Atomic actions can compete for external objects which have conventional transactional properties. This paper offers a general approach to designing distributed Coordinated Atomic action schemes and discusses the problems of action components partitioning and distribution. The approach proposed relies on using forward error recovery in the form of distributed and concurrent exception handling and resolution. After discussing the general approach, we demonstrate how it can be applied when the standard distributed model of Ada 95 is used. The presentation of the scheme is sufficiently detailed for it to be used in practice. In particular, a thorough description of the action support and all patterns (skeletons) required for designing application software are given.