Abstract
This paper presents the design and the implementation of a distributed and generic group membership algorithm. The structure of the cooperative groups is defined and modeled by graphs. The group dynamics is modeled by valid configurations that are subgroups of members in which data exchanges can occur. A group membership service and an associated protocol that manage the dynamic cooperative groups are formally specified, designed and implemented by using the Charis Actor Portfolio environment, a formal actor platform based on the statechart model that generates portable JAVA code.