Layering distributed algorithms

Superposition is a powerful program modularization and structuring method for developing parallel and distributed systems by adding new functionality to an algorithm while preserving the original computation. The superposition method will, thus, structure the distributed algorithm in a number of mechanisms on top of the original computation. In this paper the derivation using the superposition method is presented in a B-like notation explicitely expressing each new mechanism with a layer in order to improve the presentation of the superposition method. We also show that superposition refinement with layers can be used as the single formalism for developing distributed systems by using it for formalizing the derivation of a distributed load balancing algorithm of Hofstee et al. [11,12].