On semantics and refinement of UML statecharts: a coalgebraic view

Statecharts was conceived as a visual formalism for the design of reactive systems. UML statecharts is an object-based variant of classical statecharts, incorporating several concepts different from the classical statecharts. This paper discusses a coalgebraic description of UML statecharts, directly derived from its operational semantics. In particular such an approach induces suitable notions of equivalence and (behavioral) refinement for statecharts. Finally, a few refinement laws are investigated to support verifiable stepwise system development with statecharts.(undefined

Theories, Implementations, and Transformations

Abstract. The purpose of this paper is to try to put theory presentation and structuring in the simplest possible logical setting in order to improve our understanding of it. We look at how theories can be combined, and compared for strength. We look at theory refinement and implementation, and what constitutes proof of correctness. Our examples come from both the functional style and imperative (state-changing) style of theory. Finally, we explore how one implementation can be transformed to another.