A Model for Reactive Systems Supporting Varying Degrees of Synchrony

Abstract – This paper presents a model for the integration of subsystems with a varying degree of synchrony into a heteroge-nous system. While the synchronous part supports hard real-time requirements, the quasi-synchronous part is layered on a synchronous part and inherits properties like bounded drifts, bounded clock value deviation and improved failure detection. The synchronous part will be realized with a time-triggered communication system that supports also an event-triggered channel for the quasi-synchronous part. The integration of event-triggered functions with relaxed tim-ing properties makes sense if legacy systems or complex algo-rithms that cannot be temporally verified have to be used. De-pendability is preserved by the failure detector subsystem that monitors the event-triggered part and extends the fault hypoth-esis to cover also performance failures. The main benefit of the proposed architecture is the support of resource-efficient and economically feasible hard real-time dependable systems. I