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International audienceA recent trend in programming language research is to use behavioral type theory to ensure various correctness properties of largescale, communication-intensive systems. Behavioral types encompass concepts such as interfaces, communication protocols, contracts, and choreography. The successful application of behavioral types requires a solid understanding of several practical aspects, from their representation in a concrete programming language, to their integration with other programming constructs such as methods and functions, to design and monitoring methodologies that take behaviors into account. This survey provides an overview of the state of the art of these aspects, which we summarize as the pragmatics of behavioral types

We present a library for the specification and implementation of distributed protocols in native F# (and other .NET languages) based on multiparty session types (MPST). There are two main contributions. Our library is the first practical development of MPST to support what we refer to as interaction refinements: a collection of features related to the refinement of protocols, such as message-type refinements (value constraints) and message-value dependent control flow. A well-typed endpoint program using our library is guaranteed to perform only compliant session I/O actions w.r.t. to the refined protocol, up to premature termination. Second, our library is developed as a session type provider, that performs on-demand compile-time protocol validation and generation of protocol-specific .NET types for users writing the distributed endpoint programs. It is implemented by extending and integrating Scribble (a toolchain for MPST) with an SMT solver into the type providers framework. The safety guarantees are achieved by a combination of static type checking of the generated types for messages and I/O operations, correctness by construction from code generation, and automated inlining of assertions. CCS Concepts • Software and its engineering → Source code generation; • Computing methodologies → Distributed programming languages; • Networks → Peerto-peer protocols;

A recent trend in programming language research is to use behavioral type theory to ensure various correctness properties of largescale, communication-intensive systems. Behavioral types encompass concepts such as interfaces, communication protocols, contracts, and choreography. The successful application of behavioral types requires a solid understanding of several practical aspects, from their representation in a concrete programming language, to their integration with other programming constructs such as methods and functions, to design and monitoring methodologies that take behaviors into account. This survey provides an overview of the state of the art of these aspects, which we summarize as the pragmatics of behavioral types.

Fault-tolerant communication systems rely on recovery strategies which are often error-prone (e.g. a programmer manually specifies recovery strategies) or inefficient (e.g. the whole system is restarted from the beginning). This paper proposes a static analysis based on multiparty session types that can efficiently compute a safe global state from which a system of interacting processes should be recov- ered. We statically analyse the communication flow of a program, given as a multiparty protocol, to extract the causal dependencies between processes and to localise failures. We formalise our re- covery algorithm and prove its safety. A recovered communication system is free from deadlocks, orphan messages and reception er- rors. Our recovery algorithm incurs less communication cost (only affected processes are notified) and overall execution time (only required states are repeated). On top of our analysis, we design and implement a runtime framework in Erlang where failed pro- cesses and their dependencies are soundly restarted from a com- puted safe state. We evaluate our recovery framework on message- passing benchmarks and a use case for crawling webpages. The experimental results indicate our framework outperforms a built-in static recovery strategy in Erlang when a part of the protocol can be safely recovered