Distributed Timed Multitasking - A Model of Computation for Hard Real-Time Distributed Systems

The paper presents a new type of system architecture for distributed embedded systems, whereby a system is composed from embedded actors that communicate transparently by exchanging labeled messages (signals), independent of their allocation onto network nodes. Signals are exchanged at precisely specified time instants in accordance with the concept of Timed Multitasking, whereby actors can be viewed as real-time tasks with eventtriggered input and output drivers activated by timing or external events. The combination of actors, signal-based communication and timed multitasking has resulted in a new operational model Distributed Timed Multitasking (DTM). The latter has been used to derive a task execution model and requirements specifications for a real-time kernel, which have been used to develop the timed-multitasking version of the HARTEXkQWiQX. In this context, the paper presents a discussion of specific implementation issues related to the execution of periodic and sporadic tasks under DTM.