Action Systems with Synchronous Communication

The action system framework for modelling parallel and reactive programs is extended by adding procedure declarations to action systems. This permits remote procedure calls to be modelled within the framework. Synchronous message passing communication, being a special case of remote procedure calls, can therefore also be handled within this framework. This extension is done almost at no extra cost in the logical treatment of programs. The renement calculus within which the renement of action systems is formalized can be used with a minor extension to reason about action systems with procedures, as the methods are already there. The treatment of procedures was originally designed with sequential programs in mind, but is applicable to the remote procedure mechanism proposed here.