Background to NTE

Since 1992, the multicast backbone (Mbone) on the internet has been used for a large amount of multiparty multimedia conferencing experimentation. Although several audio and video tools have been developed and used on the platform, only one shared workspace tool has seen significant usage, namely the wb shared whiteboard tool from Van Jacobson of Lawrence Berkeley Labs. Although wb is a good shared whiteboard tool, we have often seen it used in circumstances where a shared text editor would have been a better choice of tool.

Wb is not a shared editor - for good reasons it keeps separate users' drawings and text separate, as this greatly simplifies both its usage and its data consistency problems. We believed that for a relatively simple environment - that of shared text editing - these consistency problems could be solved within a loose consistency framework that had excellent scaling properties similar to those of wb.

Starting from some general guiding principles - those of IP multicast, Application Level Framing and Light-weight Sessions, we set out to develop a scalable shared text editor. In this section we discuss these general guiding principles. In the next subsections, we discuss the more general requirements of a shared text editor. In section 8.3.2 we explore in detail the effects of these requirements, the development of a data model and the constraint the data distribution model places on the operations that can be performed on the data set. In section 8.3.4 we examine some more detailed issues that affect the usability of our shared text editor, and in section 8.3.6 we attempt to generalise from our experiences to see how some of the solutions might be applied elsewhere.