Structuring communication with session types

Session types are types for distributed communicating processes. They were born from process encodings of data structures and typical interaction scenarios in an asynchronous version of the π-calculus, and are being studied and developed as a potential basis for structuring concurrent and distributed computing, as well as in their own right. In this paper, we introduce basic ideas of sessions and session types, outline their key technical elements, and discuss how they may be usable for programming, drawing from our experience and comparing with existing paradigms, especially concurrent objects such as actors. We discuss how session types can offer a programming framework in which communications are structured both in program text and at run-time.