Object Inheritance Without Classes

Which comes first: the object or the class? Language designers enjoy the conceptual simplicity of object-based languages (such as Emerald or Self) while many programmers prefer the pragmatic utility of classical inheritance (as in Simula and Java). Programmers in object-based languages have a tendency to build libraries to support traditional inheritance, and language implementations are often contorted to the same end. In this paper, we revisit the relationship between classes and objects. We model various kinds of inheritance in the context of an objectoriented language whose objects are not defined by classes, and explain why class inheritance and initialisation cannot be easily modelled purely by delegation. 1998 ACM Subject Classification D.3.3 Classes and objects