When a Formal Model Rhymes with a Graphical Notation

Formal methods are based on mathematical notations which allow to rigorously reason about a model and ensure its correctness by proofs and/or model-checking. Unfortunately, these notations are complex and often difficult to understand from a human point of view especially for engineers who are not familiar with formal methods. Several research works have proposed tools to support formal models using graphical views. On the one hand, such views are useful to make formal documents accessible to humans, and on the other hand they ease the verification of some behavioral properties. However, links between graphical and formal models proposed by these approaches are often difficult to put into practice and depend on the targeted formal language. In this paper, we discuss these links from a practical approach and show how a behavioral description can be computed from a formal model based on two complementary paradigms: under-approximation (or animation-based) and over-approximation (or proof-based). We applied these paradigms in order to produce behavioural state/chart views from B models and we carried out an empirical study to assess the quality and relevance of these graphical representations for humans.