Object-Oriented Software Evolution

We review propagation patterns for describing object-oriented software at a higher level of abstraction than the one used by today's programming languages. A propagation pattern deenes a family of programs from which we can select a member by giving a class dictionary graph which details the structure of behavior through part-of and inheritance relationships between classes. The paper introduces three concepts: evolution histories, growth-plans and a propagation directive calculus. Evolution histories describe a sequence of development phases of an object-oriented program, each phase being executable and therefore testable. To keep the programs exible and short, we describe them in terms of propagation patterns. Each phase of an evolution history is tested in small steps which are constrained by class dictionary graphs belonging to a growth-plan. Propagation directives are useful both for describing propagation patterns and growth-plans and therefore we endow propagation directives with suucient expressiveness by giving a formal calculus applicable to object-oriented programming in general. A propagation directive is a succinct description of a family of submodels for a given family of data models.