Controller synthesis for stochastic hybrid switched systems, like e.g. a floor heating system in a house, is a complex computational task that cannot be solved by an exhaustive search though all the control options. The state-space to be explored is in general uncountable due to the presence of continuous variables (e.g. temperature readings in the different rooms) and even after digitization, the state-space remains huge and cannot be fully explored. We suggest a general and scalable methodology for controller synthesis for such systems. Instead of off-line synthesis of a controller for all possible input temperatures and an arbitrary time horizon, we propose an on-line synthesis methodology, where we periodically compute the controller only for the near future based on the current sensor readings. This computation is itself done by employing machine learning in order to avoid enumeration of the whole state-space. For additional scalability we propose and apply a compositional synthesis approach. Finally, we demonstrate the applicability of the methodology to a concrete floor heating system of a real family house.

We introduce the novel notion of quasi-equal clocks and use it to improve the verification time of networks of timed automata. Intuitively, two clocks are quasi-equal if, during each run of the system, they have the same valuation except for those points in time where they are reset. We propose a transformation that takes a network of timed automata and yields a network of timed automata which has a smaller set of clocks and preserves properties up to those not comparing quasi-equal clocks. Our experiments demonstrate that the verification time in three transformed real world examples is much lower compared to the original.

Abstract. We present a new decidable logic called TREX for expressing constraints about imperative tree data structures. In particular, TREX supports a transitive closure operator that can express reachability constraints, which often appear in data structure invariants. We show that our logic is closed under weakest precondition computation, which enables its use for automated software verification. We further show that satisfiability of formulas in TREX is decidable in NP. The low complexity makes it an attractive alternative to more expensive logics such as monadic second-order logic (MSOL) over trees, which have been traditionally used for reasoning about tree data structures.

The concept of hybrid automata provides a powerful framework to model and analyze real-world systems. Due to the structural complexity of hybrid systems it is important to ensure the scalability of analysis algorithms. We approach this problem by providing an effective generalisation of the recently introduced notion of quasi-equal clocks to hybrid systems. For this purpose, we introduce the concept of quasi-dependent variables. Our contribution is two-fold: we demonstrate how such variables can be automatically detected, and we present a transformation leading to an abstraction with a smaller state space which, however, still retains the same properties as the original system. We demonstrate the practical applicability of our methods on a range of industrial benchmarks.

The design of distributed, safety-critical real-time systems is challenging due to their high complexity, the potentially large number of components, and complicated requirements and environment assumptions that stem from international standards. We present a case study that shows that despite those challenges, the automated formal verification of such systems is not only possible, but practicable even in the context of small to medium-sized enterprises. We considered a wireless fire alarm system, regulated by the EN 54 standard. We performed formal requirements engineering, modeling and verification and uncovered severe design flaws that would have prevented its certification. For an improved design, we provided dependable verification results which in particular ensure that certification tests for a relevant regulation standard will be passed. In general we observe that if system tests are specified by generalized test procedures, then verifying that a system will pass any test following those test procedures is a cost-efficient approach to improve the product quality based on formal methods. Based on our experience, we propose an approach useful to integrate the application of formal methods to product development in SME.