Abstract
A distributed system is considered in an eventdriven model where states of processes transit on occurrence of events. In this paper, we discuss a peer-to-peer (P2P) model of a topic-based publish/subscribe (P2PPS) system where each peer process (peer) pi can both subscribe a subscription pi:S and publish an event message e with a publication e:P. The subscriptions and publications are specified in terms of topics, i.e. keywords. An event message e is notified to a target peer pi whose subscription pi:S includes a common keyword with the publication e:P. Each event message e carries a vector e:KV = (kv1, , kvm) of keywords k1, , km. An event message e1 causally precedes an event message e2 with respect to a subscription Si iff not only e1 causally precedes e2 but also e1:kvh