Bounded Session Types for Object Oriented Languages

Earlier work explored the introduction of session types into object oriented languages. Following the session types literature, two parties would start communicating, provided the types attached to that communication, i.e. the corresponding session types, were dual of each other. Then, the type system was able to ensure soundness, in the sense that two communicating partners were guaranteed to receive/send sequences of values following the order specified by their session types. In the current paper we improve upon our earlier work in two ways: we extend the type system to support bounded polymorphism, and we make the selection more object-oriented, so that control structures determine how to continue evaluation, depending on the class of the object being sent/received. Interestingly, although our notion of selection is more powerful than that in earlier work, the ensuing system turned out not to be more complex, except for the notion of duality, which needed to be extended, to correctly deal with bounded polymorphism, and to capture the new notion of selection. The paper contains an example, informal explanations, a formal description of the operational semantics and of type system, and a proof of subject reduction