| We propose an interactional generalisation of structured
exceptions based on the session type discipline. Interactional
exceptions allow communicating peers to asynchronously and
collaboratively escape from the middle of a dialogue to reach another
in a coordinated fashion, under an arbitrary nesting of
exceptions. New exception types guarantee communication safety, as
well as offering precise representations and type-abstraction of
advanced conversation patterns found in practice. Protocols for
coordinating normal and exceptional exit among asynchronously running
sessions are introduced. The liveness property established under
these protocols guarantees consistency of coordinated exception
handling among communicating peers. |
(Final Version)