Analysis on strategies of superposition refinement of Event-B specifications

Abstract

The superposition refinement with the Event-B modeling method is useful because it supports construction of models in multiple abstraction levels, and thus mitigates the burden of constructing rigorous models. With such a refinement mechanism, developers can choose which subset of a target system’s elements is specified in each abstraction level (refinement strategy). Although differences of refinement strategies for a model affect the complexity of modeling and verification, the effect has not been studied. We propose our automatic refinement refactoring method, which constructs abstract versions of a given Event-B model according to a refinement strategy different from the original one. We applied the refactoring method to construct various refactored versions of large Event-B models and compared them. As a result, we found that the granularity and frequently used variables are important factors for reducing the complexity. We consider the findings important to help Event-B modelers to design and change refinement strategies.