Extracting Traceability between Predicates in Event-B Refinement

Event-B requires engineers to satisfy proof obligations and inherit all predicates from abstract models while constructing concrete ones. Engineers typically derive predicates from abstract models through transformation with the intention of gradually refining the models. These kinds of intentions for refinement are essential for other engineers to understand the refinements. However, these are implicit and not directly specified in the models. Therefore, it is difficult to understand how each predicate in concrete models is obtained from the predicates in abstract models. This paper proposes an effective method of extracting these relationships. Our approach uses heuristics to avoid exhaustive matching between predicates. It tries to find a set of related predicates by tracing elements, such as variables and constants in predicates, and excluding predicates that use common variables, but differently. Our method facilitates understanding of the intentions of refinements and can be used to help reverse engineering by clarifying the relationships between predicates through refinements.