The JavaTime Approach to Mixed Hardware-Software System Design

"What has been is what will be, and what has been done is what will be done, and there is nothing new under the sun." Abstract We describe an approach for using Java as a basis for a design and specification language for embedded systems and use our JavaTime system to illustrate many of the aspects of the approach. Java is a pragmatic choice for several reasons. Since it is a member of the C " family " of languages, it is familiar to designers. Unlike C and C++, it has standard support for concurrency. Its treatment of arrays permits better static and dynamic error checking than is conveniently feasible in C and C++. Finally, while Java's expressive power is comparable to C++, it is a much simpler language, which greatly eases the task of introducing additional analysis into compilers. Successive, formal refinement is an approach we have developed for specification of embedded systems using a general-purpose programming language. Systems are formally modeled as Abstractable Reactive systems, and Java is used as the design input language. A policy-of-use is applied to Java, in the form of language usage restrictions and class-library extensions, to ensure consistency with the formal model. A process of incremental, user-guided program transformation is used to refine a Java program until it is consistent with the policy-of-use. This approach allows systems design to begin with the flexibility of a general-purpose language, followed by gradual refinement into a more restricted form necessary for specification.