From Behavioural Contracts to Session Types

We present a research trajectory of the authors and colleagues dealing with the correctness and meaningful composition of software components, trajectory that incrementally traverses successive paradigms and approaches: open distributed processing, contract based reasoning, behavioural typing and session types. This research is grounded on the foundational work of Robin Milner on processes and observation equivalence, and the followup work by De Nicola and Hennessy on testing relations. Indeed, these initial works have set benchmarks that define the meaning of behaviour, which has fostered a full body of research in concurrency and verification. Behavioural typing is one of the avenues opened by these early contributions. This paper is a brief and staged report of the research accomplished by the authors and colleagues, presented in chronological order, starting with their work on the computational model of open distributed processing and ending at their latest work on sessions for web services.