Concurrent software system design supported by SARA at the age of one

This paper presents a multilevel modeling method suitable for the design of concurrent hardware or software systems. The methodology is requirement driven and uses tools incorporated in a programming system called SARA (Systems ARchitect's Apprentice). Both top down refinement and bottom up abstraction are supported. The design of an asynchronous sender receiver illustrates the key steps in going smoothly from programming in the large to programming in the small or actual code. The same methodology can be used to design hardware systems by applying different pragmatics than those proposed for software systems. SARA consists of a set of interactive tools implemented both at UCLA and also on the MIT-Multics system. Although SARA continues in long-term development, completed design tools accessible for experimentation by authorized users at either location via the ARPANET.