A Superimposition Control Construct for Distributed Systems

A control structure called a superimposition is proposed. The structure contains schematic abstractions of processes called roletypes in its declaration. Each roletype may be bound to processes from a basic distributed algorithm, and the operations of the roletype will then execute interleaved with those of the basic processes, over the same state space. This structure captures a kind of modularity natural for distributed programming, which previously has been treated using a macro-like implantation of code. The elements of a superimposition are identified, a syntax is suggested, correctness criteria are defined, and examples are presented.