The stepwise refinement technique is studied from a mathematical point of view. A relation
of correct refinement between programs is defined, based on the principle that refinement …

A calculus of program refinements is described, to be used as a tool for the step-by-step
derivation of correct programs. A derivation step is considered correct if the new program …

The behavior of a net of interconnected, communicating processes is described in terms of
the joint actions in which the processes can participate. A distinction is made between …

Action systems provide a method to program distributed systems that emphasizes the overall
behavior of the system. System behavior is described in terms of the possible interactions (…

Action systems provide a general description of reactive systems, capable of modeling
terminating, aborting and infinitely repeating systems. Arbitrary sequential program statements …

A lattice theoretic framework for the calculus of program refinement is presented. Specifications
and program statements are combined into a single (infinitary) language of commands …

It is shown how to apply the refinement calculus to stepwise refinement of both parallel
programs and reactive programs. The approach is based on using the action systems model to …

Superposition refinement enhances an algorithm by superposing one computation mechanism
onto another mechanism, in a way that preserves the behavior of the original mechanism…

Parallel programs are described as action systems. These are basically nondeterministic do-od
programs that can be executed in both a sequential and a parallel fashion. A method for …

Nondeterminism is introduced into an ordinary iterative programming language by treating
procedure calls as nondeterministic assignment statements. The effect of such assignment …