We develop a model for timed, reactive computation by extending the asynchronous, untimed concurrent constraint programming model in a simple and uniform way. In the spirit of process algebras, we develop some combinators expressible in this model, and reconcile their operational, logical and denotational character. We show how programs may be compiled into finite-state machines with loop-free computations at each state, thus guaranteeing bounded response time. 1 Introduction and Motivation Reactive systems [12,3,9] are those that react continuously with their environment at a rate controlled by the environment. Execution in a reactive system proceeds in bursts of activity. In each phase, the environment stimulates the system with an input, obtains a response in bounded time, and may then be inactive (with respect to the system) for an arbitrary period of time before initiating the next burst. Examples of reactive systems are controllers and signal-processing systems. The primary issu..
