Preface of Proceedings Third Workshop on Behavioural Types, BEAT 2014, Rome, Italy, 1st September 2014

This volume contains the proceedings of BEAT 2014, the third Workshop on Behavioural Types. The workshop took place in Rome, Italy, on September 1st 2014, as a satellite even of CONCUR 2014, the 25th International Conference on Concurrency Theory. The aim of this workshop is to bring together researchers in all aspects of behavioural type theory and its applications, in order to share results, consolidate the community, and discover opportunities for new collaborations and future directions

Reversibility in session-based concurrency: A fresh look

Much research has studied foundations for correct and reliable communication-centric software systems. A salient approach to correctness uses verification based on session types to enforce structured communications; a recent approach to reliability uses reversible actions as a way of reacting to unanticipated events or failures. In this paper, we develop a simple observation: the semantic machinery required to define asynchronous (queue-based), monitored communications can also support reversible protocols. We propose a framework of session communication in which monitors support reversibility of (untyped) processes. Main novelty in our approach are session types with present and past, which allow us to streamline the semantics of reversible actions. We prove that reversibility in our framework is causally consistent, and define ways of using monitors to control reversible actions. Keyword

Comparing type systems for deadlock freedom

Message-passing software systems exhibit non-trivial forms of concurrency and distribution; they are expected to follow intended protocols among communicating services, but also to never “get stuck”. This intuitive requirement has been expressed by liveness properties such as progress or (dead)lock freedom and various type systems ensure these properties for concurrent processes. Unfortunately, very little is known about the precise relationship between these type systems and the classes of typed processes they induce. This paper puts forward the first comparative study of different type systems for message-passing processes that guarantee deadlock freedom. We compare two classes of deadlock-free typed processes, here denoted L and K. The class L stands out for its canonicity: it results from Curry-Howard interpretations of classical linear logic propositions as session types. The class K, obtained by encoding session types into Kobayashi’s linear types with usages, includes processes not typable in other type systems. We show that L is strictly included in K, and identify the precise conditions under which they coincide. We also provide two type-preserving translations of processes in K into processes in L