Fundamentals of session types

Abstract

We present a reconstruction of session types in a linear pi calculus where types are qualified as linear or unrestricted. Linearly qualified communication channels are guaranteed to occur in exactly one thread, possibly multiple times. In our language each channel is characterised by two distinct variables, one used for reading, the other for writing; scope restriction binds together two variables, thus establishing the correspondence between the two ends of a same channel. This mechanism allows a precise control of resources via a linear type system. We build the language gradually, starting from simple input/output, then adding choice, recursive types, replication and finally subtyping. We also present an algorithmic type checking system. © 2009 Springer.