Refactoring Object-Oriented Specifications with Inheritance-Based Polymorphism

Specification notations such as JML and Spec# which are embedded into program code provide a promising approach to formal object-oriented software development. If the program code is refactored, however, the specifications need also to be changed. This can be facilitated by specification refactoring rules which allows such changes to be made systematically along with the changes to the code. A set of minimal and complete set of refactoring rules have been devised for the Object-Z specification language. This paper reviews these rules as a basis for a similar approach for languages like JML and Spec#. Specifically, it modifies the rules for introducing and removing inheritance and polymorphism from specifications. While these concepts are orthogonal in Object-Z, they are closely intertwined in the other notations.