Parallel Refinement Mechanisms for Real-Time Systems

This paper discusses highly general mechanisms for specifying the refinement of a real-time system as a collection of lower level parallel components that preserve the timing and functional requirements of the upper level specification. These mechanisms are discussed in the context of ASTRAL, which is a formal specification language for real-time systems. Refinement is accomplished by mapping all of the elements of an upper level specification into lower level elements that may be split among several parallel components. In addition, actions that can occur in the upper level are mapped to actions of components operating at the lower level. This allows several types of implementation strategies to be specified in a fairly natural way, while the price for generality (in terms of complexity) is paid only when necessary. The refinement mechanisms are illustrated using a simple digital circuit and a much more complex example is sketched.