Embedded real-time systems often operate under strict timing and dependability constraints. To ensure responsiveness, these systems must be able to provide the expected services in a timely manner even in the presence of faults. In this paper, we describe a run-time environment for monitoring of timing constraints in distributed real-time systems. In particular, we focus on the problem of detecting violations of timing assertions in an environment in which the real-time tasks run on multiple processors, and timing constraints can be either inter-processor or intra-processor constraints. Constraint violations are detected at the earliest possible time by deriving and checking intermediate constraints from the user-specified constraints. If the violations must be detected as early as possible, then the problem of minimizing the number of messages to be exchanged between the processors becomes intractable. We characterize a sub-class of timing constraints that occur commonly in distributed real-time systems and whose message requirements can be minimized. We also take into account the drift among the various processor clocks when detecting a violation of a timing assertion. Finally, we describe a prototype implementation of a distributed rim-time monitor.

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Embedded real-time systems often operate under strict timing and dependability constraints. To ensure responsiveness, these systems must be able to provide the expected services in a timely manner even in the presence of faults. In this paper, we describe a run-time environment for monitoring of timing constraints in distributed real-time systems. In particular, we focus on the problem of detecting violations of timing assertions in an environment in which the real-time tasks run on multiple processors, and timing constraints can be either inter-processor or intra-processor constraints. Constraint violations are detected at the earliest possible time by deriving and checking intermediate constraints from the user-specified constraints. If the violations must be detected as early as possible, then the problem of minimizing the number of messages to be exchanged between the processors becomes intractable. We characterize a sub-class of timing constraints that occur commonly in distributed real-time systems and whose message requirements can be minimized. We also take into account the drift among the various processor clocks when detecting a violation of a timing assertion. Finally, we describe a prototype implementation of a distributed rim-time monitor.

We describe a toolset, consisting of a graphical editor, a simulator, and an assertion checker, for prototyping real‐time systems that are specified as Communicating Real‐Time State machines (CRSMs). CRSMs are timed state machines that communicate synchronously over unidirectional channels. The system behavior of CRSMs is characterized by a time‐stamped trace of communication events. Safety and timing assertions on the trace of communication events are expressed in a notation based on Real‐Time Logic. We illustrate the simulator and assertion checker by specifying a traffic‐light controller and other real‐time systems. There are two main contributions in this work: first, the prototyping environment serves as a validation of the model, the execution algorithm and paper design of example CRSMs, demonstrating that the ideas are realizable and potentially useful. Secondly, the paper presents a novel and useful method of specifying safety and timing properties, and checking them during simulation.

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