Privacy via Subsumption

We describe an object calculus allowing object extension and structural subtyping. Each object has a “dictionary” to mediate the connection between names and components. This extra indirection yields the first object calculus combining both object extension and full width subtyping in a type-safe manner. If class inheritance is modeled with object extension, private fields and methods can be achieved directly by scoping restrictions: private fields or methods are those hidden by subsumption. We prove that the type system is sound, discuss a variant allowing covariant self types, and give some examples of the expressiveness of the calculus.

Authors

• Jon G. Riecke
• Christopher A. Stone

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