Verifying worst-case execution time of timed automata models with cyclic behaviour

Omar Bataineh

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated] The thesis presents novel zone-based algorithms for computing worst case execution time (WCET) or maximum termination time of real-time systems using the timed automata (TA) model checking technology. The algorithms can work on any arbitrary diagonal-free TA 1 and can handle more cases than previously existing algorithms for WCET computations, as it can handle cycles in TA and decide whether they lead to an innite WCET. We show soundness of the proposed algorithms and study their complexity. The solutions provided here are conceptually a marked improvement over some earlier work on the problem, in which repeated guesses(guided by binary search) and multiple model checking queries were effectively but inelegantly and less efficiently used; here only one run of the zone construction is sufficient to yield the answers.

    The thesis also proposes a set of acceleration techniques that improve the efficiency of WCET verification of TA with cyclic behaviour. We prove that the proposed accelerations are exact with respect to the WCET problem and demonstrate that model checking WCET with the proposed acceleration techniques can significantly speed-up the verification of WCET of real-time systems. We also compare our algorithm with the one implemented in the model checker UPPAAL which shows that the proposed algorithms can handle cases that UPPAAL fails to verify, where we show that in certain circumstances, when innite cycles exist, UPPAAL's algorithm may not terminate, and when largely repetitivefinite cycles exist, UPPAAL's algorithm suffers from the state space explosion, thus leading to a low efficiency or resource exhaustion.


    1The diagonal-free TA is a class of TA in which the test of the form - y  ˜c is disallowed, where x, y are clocks, c is a constant, and ˜ϵ {<,≤,=,>,≥}.














    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - Jul 2015

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