Recent results of distributed systems research, in multicasting and group oriented communication systems and protocols, are very attractive to implement multiparticipant and collaborative applications. In this paper, we examine the requirements and criteria placed by large scale cooperative applications, namely those alternating multiparticipant synchronous work sessions with asynchronous interactions and disconnected work. We propose a topology organization, an architectural model and the materialization of an integrated generic platform to support those requirements. We argue on the necessary evolution from the well known client/server model to new paradigms involving collaborative-object-group orientation. We describe the implementation of an object-group-oriented infrastructure as well as a generic programming framework offering high flexibility(1).