Moderated group authoring among weakly connected workgroups

Our goal is to develop a practical groupware system that allows any group member to modify a shared file. Each user can modify any part of the document; the documents cannot be easily decomposed into sections that can be independently modified. Updates from different users will conflict and the goal is to resolve these conflicts and eventually produce a consistent document. Consider a group of users: Alice, Bob and Tom who are modifying a single document (illustrated in Figure 1). Each user creates updates on a shared document: Alice creates updates a1, a2, and a3, Bob creates b1 and b2 and Tom creates updates t1, t2 and t3. Traditionally, groupware systems ordered these updates using their causality relationships [1] in order to achieve consistency. The updates are then applied in this particular order. However, the system performance and the duration for all the updates to be applied to produce a consistent version depends on the availability patterns of the group members.