Reversible Multiparty Sessions with Checkpoints

Reversible interactions model different scenarios, like biochemical systems and human as well as automatic negotiations. We abstract interactions via multiparty sessions enriched with named checkpoints. Computations can either go forward or roll back to some checkpoints, where possibly different choices may be taken. In this way communications can be undone and different conversations may be tried. Interactions are typed with global types, which control also rollbacks. Typeability of session participants in agreement with global types ensures session fidelity and progress of reversible communications.Comment: In Proceedings EXPRESS/SOS 2016, arXiv:1608.0269

Liveness of Communicating Transactions (Extended Abstract)

We study liveness and safety in the context of CCS extended with communicating transactions, a construct we recently proposed to model automatic error recovery in distributed systems. We show that fair-testing and may-testing capture the right notions of liveness and safety in this setting, and argue that must-testing imposes too strong a requirement in the presence of transactions. We develop a sound and complete theory of fair-testing in terms of CCS-like tree failures and show that, compared to CCS, communicating transactions provide increased distinguishing power to the observer. We also show that weak bisimilarity is a sound, though incomplete, proof technique for both may- and fairtesting. To the best of our knowledge this is the first semantic treatment of liveness in the presence of transactions. We exhibit the usefulness of our theory by proving illuminating liveness laws and simple but nontrivial examples