Coordinator: a basic building block for multimedia conferencing systems

An architectural model that allows the construction of multimedia conferencing environments on the basis of a set of basic building blocks is defined. A coordinator is a basic building block for designing and implementing conferencing systems. It controls the activities of a set of cooperating users. It is based on the different roles played by groups of conference attendants and describes the conference behavior in terms of role changes. Different coordinators correspond to different abstractions of a cooperative activity: multiplexing of data streams, floor control for a conversation, overall conference management, and so on. Each coordinator encapsulates specific issues, such as device and media dependencies, application-dependent behaviors, and user-oriented strategies. A cooperative environment is built bottom-up by connecting controllers in a hierarchical control structure