Specification and verification of the Co4 distributed knowledge system using LOTOS

This paper relates the formal specification and verification of a consensual decision protocol based on Co₄, a computer environment dedicated to the building of a distributed knowledge base. This protocol has been specified in the ISO formal description technique LOTOS. The CADP tools from the EUCALYPTUS LOTOS toolset have been used to verify different safety and liveness properties. The verification work has confirmed an announced violation of knowledge consistency and has put forth a case of inconsistent hierarchy, four cases of unexpected message reception and some further local corrections in the definition of the protocol