Maintaining Consistency Over A Network in Real-Time Applications

In a large class of hard-real-time control applications, components execute concurrently on distributed nodes and periodically coordinate, under timing constraints, to perform the control task. As such, they perform a type of atomic commitment. Traditional atomic commitment differs, however, because there is no notion of a deadline. We therefore present a model and correctness criteria for timed atomic commitment (TAC) which requires the processes to be functionally consistent, but allows the outcome to include an exceptional state, indicating that timing constraints have been violated. An extension to accomodate the periodic behavior frequently found in control applications is then discussed, and a decentralized implementation is outlined. We conclude by presenting language constructs for these features, and illustrate their use with an example.