Re-designing Tasking Structures of Ada Programs for Analysis: A Case Study

In YY91, YY93b, Yeh93] we described a compositional (hierarchical) approach to reachability analysis of Ada tasking programs based on process algebra. The abstraction capabilities of process algebra provide an eeective means to control state explosion in automated state-space analysis, but only if a design is carefully modularized to encapsulate details of behavior. We report here our experience modifying an existing design (the remote temperature sensor system described in San89]) to make it more amenable to hierarchical analysis. Redesign for analysis was eeective in improving the design in other ways as well: Flaws uncovered in the analysis (and present in the original design) were easy to understand and correct because of the increased understandability of the revised design. This also suggests that these aws might have been avoided, and the design generally improved, had \design for analysis" been applied from the start.