Massimo Bartoletti, Laura Bocchi, and Maurizio Murgia
Abstract. We develop a theory of refinement for timed asynchronous systems, in the setting of Communicating Timed Automata (CTA). Our refinement applies point-wise to the components of a system of CTA, and only affecting their time constraints - in this way, we achieve compositionality and decidability. We then establish a decidable condition under which our refinement preserves behavioural properties of systems, such as their global and local progress. Our theory provides guidelines on how to implement timed protocols using the real-time primitives of programming languages. We validate our theory through a series of experiments, supported by an open-source tool which implements our verification techniques.
Laura Bocchi, Maurizio Murgia, Vasco Thudichum Vasconcelos, and Nobuko Yoshida
Abstract. We present a behavioural typing system for a higher-order timed calculus, using types to model timed protocols (i.e., application-level specifications of interaction patterns among distributed applications), and a calculus to abstract implementations. Behavioural typing ensures that processes in the calculus will perform actions in the time-windows prescribed by their protocols. We introduce duality and subtyping for timed asynchronous session types. Duality includes a class of protocols that previous work on asynchronous timed session types could not type-check. Subtyping is critical for precision of our typing system, especially for session delegation. The composition of dual (timed asynchronous) types enjoys progress when using an urgent receive semantics, in which receive actions are executed as soon as the expected message is available. Our calculus increases the modelling power of calculi used in the previous work on timed sessions, adding a blocking receive primitive with timeout, and a primitive that consumes an arbitrary amount of time in a given range.
Maurizio Murgia
Abstract. We study an urgent semantics of asynchronous timed session types, where input actions happen as soon as possible. We show that with this semantics we can recover to the timed setting an appealing property of untimed session types: namely, deadlock-freedom is preserved when passing from synchronous to asynchronous communication.