Using Deadline Commands to Reason about Non-terminating Loops Using Deadline Commands to Reason about Non-terminating Loops

It is common for a real-time process to consist of a nonterminating loop monitoring an input and controlling an output. Hence a real-time program development method needs to support nonterminating loops. Earlier work on real-time program development has produced a real-time reenement calculus that makes use of a novel deadline command which allows timing constraints to be embedded in real-time programs. The addition of the deadline command to the real-time programming language gives the signiicant advantage of having a real-time programming language that is machine independent. This allows a more abstract approach to the program development process. In this paper we add possibly nonterminating loops to the reenement calculus. First we examine the semantics of possibly nonterminating loops, and use them to reason directly about a simple example. Then we develop simpler reenement rules that make use of a loop invariant.