Reasoning About Inheritance and Unrestricted Reuse in Object-Oriented Concurrent Systems

Code reuse is a fundamental aspect of object-oriented programs, and in particular, the mechanisms of inheritance and late binding provide great flexibility in code reuse, without semantical limitations other than typecorrectness. However, modular reasoning about late binding and inheritance is challenging, and formal reasoning approaches place semantical restrictions on code reuse in order to preserve properties from superclasses. The overall aim of this paper is to develop a formal framework for modular reasoning about classes and inheritance, supporting unrestricted reuse of code, as well as of specifications. The main contribution is a Hoarestyle logic supporting free reuse, worked out for a high-level concurrent object-oriented language. We also show results on verification reuse, based on a combination of Hoare-style logic and static checking. An example illustrates the difference to comparable reasoning formalisms.