Inheritance Decomposed Position Paper

Inheritance is often portrayed as a fundamental ingredient of object-oriented programming, one which is essential to building extensible software systems. However, inheritance is also a controversial mechanism with many competing and often contradictory interpretations, whose use can even impede extensibility in certain scenarios. Decomposing inheritance into the more basic mechanisms of object composition and message forwarding solves many of these problems. The resulting programming model is simpler yet more flexible than one based on inheritance, and illustrates that inclusion polymorphism is actually the more fundamental ingredient.