A Model for Real-Time Co-operation

This paper introduces a general model for both specifying and designing conferences. A major goal of the model is to be useful at both the specification and the design stage. The model follows an object-oriented approach. It is based on the different roles played by groups of conference attendants, and describes conference behaviour in term of role changes. Groups are defined at different abstraction levels. Specific activities (multiplexing of data streams, floor-control for a conversation, overall conference management) are driven by coordinators. They encapsulate different aspects, such as: deviceand media-dependencies, application-dependent behaviours and user oriented strategies. Coordinators can be combined in a hierarchical control structure.