On the Specification of Partitionable Group Membership

Group communication in partitionable systems has been the focus of many research activities over the last decade. Fault-tolerant applications in a partitionable system model generally rely on two basic services: a group membership service and a reliable multicast service. The paper considers two of the most prominent specifications for such services that appear in the literature. Based on these specifications, the paper shows that one specification can be satisfied by a trivial implementation and the other, which basically extends the first one, requires additional system assumptions, which are discussed in the paper. The paper shows that the specifications of group communication in partitionable systems has not yet reached the level of maturity of the so called primary partition specifications.