Behavioural Prototypes

Concurrent objects andmultiparty compatibility. Data types describe values; behavioural types such as multiparty session types [4] and typestate [3] describe interactions. Here we introduce a simple actor language and show how multiparty compatibility [1] can be used to statically type-check systems of concurrent objects whose interfaces evolve dynamically in response to messages. Our program in our language is a collection of communicating automata [2]. An asynchronous send of message m(v) to p is written p!m(v). A blocking receive from p is written p?m(v), and binds the parameter v to the value sent. Our example models a simple software development workWow with four mutually recursive roles. The wavy underlining can be ignored for the moment. In the code below, the teamLead starts the devTeam and then begins a ReleaseCycle. Once a release candidate at revision v is received from the devTeam, the business is informed. If the business accepts the release, it is tagged by the teamLead and the devTeam can stop. Alternatively the business can request another iteration, and the cycle repeats.