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Verifying Asynchronous Interactions via Communicating Session Automata

Julien LANGE, Nobuko YOSHIDA

The relationship between communicating automata and session types is the cornerstone of many diverse theories and tools, including type checking, code generation, and runtime verification. A serious limitation of session types is that, while endpoint programs interact asynchronously, the underlying property which guarantees safety of session types is too synchronous: it requires a one-to-one synchronisation between send and receive actions. This paper proposes a sound procedure to verify properties of communicating session automata (CSA), i.e., communicating automata that correspond to multiparty session types. We introduce a new asynchronous compatibility property for CSA, called k-multiparty compatibility (k-MC), which is a strict superset of the synchronous multiparty compatibility proposed in the literature. It is decomposed into two bounded properties: (i) a condition called k-safety which guarantees that, within the bound, all sent messages can be received and each automaton can make a move; and (ii) a condition called k-exhaustivity which guarantees that all k-reachable send actions can be fired within the bound. We show that k-exhaustive systems soundly and completely characterise systems where each automaton behaves uniformly for any bound greater or equal to k. We show that checking k-MC is PSPACE-complete, but can be done efficiently over large systems by using partial order reduction techniques. We demonstrate that several examples from the literature are k-MC, but not synchronous compatible.

@inproceedings{LY2019,
  author = {Julien Lange and Nobuko Yoshida},
  title = {{Verifying Asynchronous Interactions via Communicating Session Automata}},
  booktitle = {31st International Conference on Computer-Aided Verification},
  series = {LNCS},
  volume = {11561},
  pages = {117--97},
  publisher = {Springer},
  year = 2019
}

@inproceedings{LY2019,
  author = {Julien Lange and Nobuko Yoshida},
  title = {{Verifying Asynchronous Interactions via Communicating Session Automata}},
  booktitle = {31st International Conference on Computer-Aided Verification},
  series = {LNCS},
  volume = {11561},
  pages = {117--97},
  publisher = {Springer},
  doi = "10.1007/978-3-030-25540-4 6",
  year = 2019
}