On requirement verification for evolving Statecharts specifications

Abstract

Software development processes have been evolving from rigid, pre-specified, and sequential to incremental, and iterative. This evolution has been dictated by the need to accommodate evolving user requirements and reduce the delay between design decision and feedback from users. Formal verification techniques, however, have largely ignored this evolution and even when they made enormous improvements and found significant uses in practice, like in the case of model checking, they remained confined into the niches of safety-critical systems. Model checking verifies if a system’s model $\mathcal{M}$ satisfies a set of requirements, formalized as a set of logic properties $\Phi$. Current model-checking approaches, however, implicitly rely on the assumption that both the complete model $\mathcal{M}$ and the whole set of properties $\Phi$ are fully specified when verification takes place. Very often, however, $\mathcal{M}$ is subject to change because its development is iterative and its definition evolves through stages of incompleteness, where alternative design decisions are explored, typically to evaluate some quality trade-offs. Evolving systems specifications of this kind ask for novel verification approaches that tolerate incompleteness and support incremental analysis of alternative designs for certain functionalities. This is exactly the focus of this paper, which develops an incremental model-checking approach for evolving Statecharts. Statecharts have been chosen both because they are increasingly used in practice natively support model refinements.