Behavioral composition for compatible software module evolution

Abstract

Inheritance mechanism has been suggested as a good solution for incremental modification in object-oriented development. However, inheritance without compatibility causes poor readability of a program, makes the maintenance of a software module difficult, and often leads to unexpected behavior. Therefore, it is important to guarantee behavior compatibility. In this thesis, we propose a mechanism for compatible software module evolution using composition rules in terms of statechart. There are two kinds of composition rules. One is mixin rule that is used as white-box composition. Using the mixin rules, designers can make variations of an object. The other is delegation rule that is used as black-box composition, and designers can compose objects without knowing the internal structure of the objects. The composition rules guarantee some level of compatibility between supertypes and subtypes on subtyping. This work addresses the composition of existing different objects, while previous work mainly focused on specialization and life cycle of an object. This work also provides the basis of automatic construction of software modules at design stage.