Partial order reductions have been successfully applied to model checking of concurrent systems and practical applications of the technique show nontrivial reduction in the size of the explored state space. We present a theory of partial order reduction based on stubborn sets in the game-theoretical setting of 2-player games with reachability/safety objectives. Our stubborn reduction allows us to prune the interleaving behaviour of both players in the game, and we formally prove its correctness on the class of games played on general labelled transition systems. We then instantiate the framework to the class of weighted Petri net games with inhibitor arcs and provide its efficient implementation in the model checker TAPAAL. Finally, we evaluate our stubborn reduction on several case studies and demonstrate its efficiency.

Partial order reduction for timed systems is a challenging topic due to the dependencies among events induced by time acting as a global synchronization mechanism. So far, there has only been a limited success in finding practically applicable solutions yielding significant state space reductions. We suggest a working and efficient method to facilitate stubborn set reduction for timed systems with urgent behaviour. We first describe the framework in the general setting of timed labelled transition systems and then instantiate it to the case of timed-arc Petri nets. The basic idea is that we can employ classical untimed partial order reduction techniques as long as urgent behaviour is enforced. Our solution is implemented in the model checker TAPAAL and the feature is now broadly available to the users of the tool. By a series of larger case studies, we document the benefits of our method and its applicability to real-world scenarios.

Floor heating systems are important components of nowadays home-automation setups. The control of a floor heating system is a nontrivial task and the present solutions essentially implement variants of a simple bang-bang controller that opens for a hot water circulation in a room if its current temperature is below the user defined target temperature, otherwise it closes for the heating in the room. The disadvantage is that the heat exchange among the rooms, outside weather conditions, weather forecast and other factors are not considered. We propose a novel model-driven approach for intelligent floor heating control based on a chain of tools that allow us to gather the sensor readings from the actual hardware and use the state-of-the-art controller synthesis tool UPPAAL Stratego in order to synthesise abstract control strategies that are then executed on the real hardware platform provided by the company Seluxit. We have built a scaled demonstrator of the system and the experimental results document a 38% to 52 % increase in user satisfaction, moreover with additional energy savings between 2% to 12%.

Abstract 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.

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.