Systematic program development

A constructive method of program development is presented. It is based on a simple strategy for problem decomposition that is claimed to be more supportive of goal-oriented programming than the Wirth-Dijkstra top-down refinement method. With the proposed method, a program is developed by making a sequence of refinements, each of which can establish the postcondition for a corresponding sequence of progressively weaker preconditions until a mechanism has been composed that will establish the postcondition for the original given precondition for the problem. The strategy can minimize case analysis, simplify constructive program proofs, and ensure a correspondence between program structure and data structure