Reentrant Statecharts for Concurrent Real-Time Systems

In this paper, we present novel notions of reentrant state machines and reentrant statecharts, which are extensions of traditional state machines and statecharts with the addition of concurrent syntax and semantics. Reentrant state machines can provide efficient concurrency support for statechart-based real-time tasks by interleaving the execution of concurrent tasks. With its well-defined syntax and semantics, the reentrant state machine is able to switch among tasks on an eventby-event basis. By keeping track of task-specific information about concurrent tasks, the reentrant state machine can ensure correct order-dependent state transitions for each individual task. Based on the notion of reentrant state machines, reentrant statecharts provide a compact and highly expressive means for constructing detailed concurrent behavior models.