A Sound and Complete Projection for Global Types

Multiparty session types is a typing discipline used to write specifications, known as global types, for branching and recursive message-passing systems. A necessary operation on global types is projection to abstractions of local behaviour, called local types. Typically, this is a computable partial function that given a global type and a role erases all details irrelevant to this role. Computable projection functions in the literature are either unsound or too restrictive when dealing with recursion and branching. Recent work has taken a more general approach to projection defining it as a coinductive, but not computable, relation. Our work defines a new computable projection function that is sound and complete with respect to its coinductive counterpart and, hence, equally expressive. All results have been mechanised in the Coq proof assistant

VeriMon: A Formally Verified Monitoring Tool

A runtime monitor observes a running system and checks whether the sequence of events the system generates satisfies a given specification. We describe the evolution of VeriMon: an expressive and efficient monitor that has been formally verified using the Isabelle proof assistant.ISSN:0302-9743ISSN:1611-334