The Timer Cascade: Functional Modelling and Real Time Calculi

Case studies can significantly contribute towards improving the understanding of formalisms and thereby to their applicability in practice. One such case, namely a cascade of the familiar 24-hour timers (in suitably generalized form) provides interesting gedanken experiments and illustrations for presenting, illustrating and comparing various formalisms for modelling real-time behaviour of systems. The timer cascade is first modelled in a general-purpose functional formalism (Funmath) and various properties are derived, including an interesting algebraic monoid structure of timer programs. Then it is described and analyzed in duration calculus, thereby highlighting, similarities and differences in the approach to modelling and reasoning, and also the link between the formalisms. Future work consists in using this case as a running example for exploring the same issues for other formalisms intended for real time and hybrid systems. The underlying idea is that other authors join this effort and contribute towards extending it, finally arriving at a broad comparative survey of such formalisms. Index terms — Automata, cascade connection, Duration Calculus, functional description, Funmath, hybrid systems, real time systems, systems modelling, timers