The design of inheritance and encapsulation in Self, an object-oriented language based on prototypes, results from understanding that inheritance allows parents to be shared parts of their children. The programmer resolves ambiguities arising from multiple inheritance by prioritizing an object’s parents. Unifying unordered and ordered multiple inheritance supports differential programming of abstractions and methods, combination of unrelated abstractions, unequal combination of abstractions, and mixins. In Self, a private slot may be accessed if the sending method is a shared part of the receiver, allowing privileged communication between related objects. Thus, classless Self enjoys the benefits of class-based encapsulation.
Lisp and Symbolic Computation 4(3), Kluwer Academic Publishers, June, 1991.