In the context of a groupware system, latecomers are individuals that join a session after a session has started. Typically, a user begins a collaborative session in groupware. To participate in a session, latecomers require a shared state.
A groupware system requires a basic mechanism that allows latecomers to attain a system's current state via a replay describing how a current state was attained. This mechanism logs modifying events in a history list. This list is replayed to latecomers with a current activity status. If an event depends on external information, it can be difficult to replay a log correctly.
Maintaining history can present two key issues:
It can potentially consume too much memory space.
A complete replay consumes time.
A replay alternative is a direct state transfer from a supporting site to a latecomer site, which provides latecomer updates more efficiently. If a shared state is maintained, it is easy to support a latecomer with the current state. However, this task becomes difficult if a shared thread is completely or partially replicated.