Augmented state-transition diagrams for reactive software

Abstract

The state transition diagram (STD) was invented in the '50's at Bell Laboratories to solve process control problems related to switching of telephone calls. This graphic technique, while extraordinarily descriptive and mathematically rigorous, was very expensive to maintain manually. The technique fell into disuse when tabular techniques were developed and taught to the new generation of electrical engineers. When modern interactive graphics are applied to the technique, and when the basic model is augmented with a simple graphic notation which allows both event processing and logical branching on system conditions, the augmented state transition diagram becomes a powerful CASE tool which is useful across most of the software life cycle.