27-10-2014, 11:06 AM
Abstracts: Correct implementation of general real-time applications remains by far an open problem. A key issue is meeting timing constraints whose satisfaction depends onfeatures of the execution platform, in particular its speed.Existing rigorous implementation techniques are applicableto specific classes of systems e.g. with periodic tasks, time deterministic systems. We present a general model-based implementation method for real-time systems based on the use of two models. An abstract model representing the behavior of real-timesoftware as a timed automaton. The latter describesuser-defined platform-independent timing constraints. Its transitions are timeless and correspond to the executionof statements of the real-time software.A physical model representing the behavior of the real-time software running on a given platform. It is obtained by assigning execution times to the transitions of the abstract model. A necessary condition for implement ability is time-safety that is, any (timed) execution sequence of the physical models also an execution sequence of the abstract model. Time-safety simply means that the platform is fast enough to meetthe timing requirements. As execution times of actions arenot known exactly, time-safety is checked for worst-case execution times of actions by making an assumption of time-robustness: time-safety is preserved when speed of execution platform increases.