Direct methods for deductive verification of temporal properties in continuous dynamical systems
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This thesis is concerned with the problem of formal verification of correctness specifications for continuous and hybrid dynamical systems. Our main focus will be on developing and automating general proof principles for temporal properties of systems described by non-linear ordinary differential equations (ODEs) under evolution constraints. The proof methods we consider will work directly with the differential equations and will not rely on the explicit knowledge of solutions, which are in practice rarely available. Our ultimate goal is to increase the scope of formal deductive verification tools for hybrid system designs. We give a comprehensive survey and comparison of available methods for checking set invariance in continuous systems, which provides a foundation for safety verification using inductive invariants. Building on this, we present a technique for constructing discrete abstractions of continuous systems in which spurious transitions between discrete states are entirely eliminated, thereby extending previous work. We develop a method for automatically generating inductive invariants for continuous systems by efficiently extracting reachable sets from their discrete abstractions. To reason about liveness properties in ODEs, we introduce a new proof principle that extends and generalizes methods that have been reported previously and is highly amenable to use as a rule of inference in a deductive verification calculus for hybrid systems. We will conclude with a summary of our contributions and directions for future work.