The system is described in three main parts: The user interface, the distribution mechanism for users' contributions and the floor control scheme. The central purpose of this section is to present as complete a model of floor control as possible, so that implementors of conferencing systems have a general framework from which to derive any specific policies they require. Underlying mechanisms are emerging for multi-destination delivery of data. We see how these can be used by the conferencing system. Higher level tools are now available to help specify the set of distributed operations in a system. We have used these to decompose the various control messages and flow of users data around the conference.