Specification and Verification of the Co4 Distributed Knowledge System using LOTOS

This report presents the speciication and veriication of a consensual decision protocol used in Co 4 , a computer environment dedicated to the building of a distributed knowledge base. This protocol has been speciied in the Iso formal description technique Lotos. The Cadp tools from the Eucalyptus Lotos toolset have been used to verify diierent safety and liveness properties. The veriication work has connrmed 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 deenition of the protocol. The full commented Lotos speciication and excerpts from detailed results are included in appendices. Spciication et vriication du systtme de connaissances distribuu Co4 en LOTOS RRsumm : Ce rapport relate la spciication et la vriication d'un protocole de ddcision consensuelle utiliss dans Co 4 , un environnement informatique dddii la construction d'une base de connaissances distribuue. Ce protocole a tt spciii en Lotos, une technique de description formelle normalisse par l'Iso. Les outils Cadp de la boote outils Eucalyptus ont tt utilisss pour vriier diiirentes propriitts de ssrett et de vivacitt. Ce travail de vriication a connrmm une violation connue de consistance de la connaissance et a mis en vidence un cas de hiirarchie inconsistante, quatre cas de rrception non prrvue de message et plusieurs autres corrections locales dans la dddnition du protocole. La spciication Lotos compllte et commentte et certains extraits des rrsultats ddtaillls gurent en appendices.