Shared window systems enable existing applications to be shared in the context of a real-time teleconference. The development and successful use of several such systems, albeit within limited user communities, testifies to the merits of the basic idea. However, experience to date has suggested a number of areas that have not been adequately addressed, namely: spontaneous interactions, shared workspace management, floor control, and annotation and telepointing. This paper focuses on the ramifications, for the software designer, of various user requirements in these areas. While the recommendations that result are motivated by the desire to enable continued use of collaboration-transparent applications, addressing them involves the development of systems software that is distinctly collaboration-aware.

Replicating applications in a shared window environment can significantly improve the performance of the resulting system. Compared to a completely centralized approach, a replicated architecture offers superior response time and reduces network load. To date, however, these advantages have been overshadowed by the equally significant synchronization problems associated with replication. In this paper we document these problems and show that the most frequent synchronization problems can be solved without changing existing software. We further indicate how some of the limitations of the resulting system can lx removed by making applications or system servers collaboration-aware. Finally, we point out where general system support is needed to address the remaining deficiencies.

Replicating applications in a shared window environment can significantly improve the performance of the resulting system. Compared to a completely centralized approach, a replicated architecture offers superior response time and reduces network load. To date, however, these advantages have been overshadowed by the equally significant synchronization problems associated with replication. In this paper we document these problems and show that the most frequent synchronization problems can be solved without changing existing software. We further indicate how some of the limitations of the resulting system can be removed by making applications or system servers collaboration-aware. Finally, we point out where general system support is needed to address the remaining deficiencies.