Mobile technology is particularly suited to a fully distributed (replicated) architecture for collaborative work. Users can maintain their own document copies, and can continue to work in the absence of a central server. However, in a replicated architecture, conflicts can occur when two or more users concurrently modify the same object in a shared document. Such conflicts can be classified as non-exclusive or exclusive.
Non-exclusive conflicts, where conflicting operations can be realized at the same time, can be handled using conventional consistency management techniques such as operational transformation. On the other hand, exclusive conflicts can only be realised in different document versions. Although post-locking (Xue, Zhang, and Sun 2001) can be used to limit the number of versions that are created and thus reduce storage requirements in constrained mobile devices, it introduces two problems: a partial-intention problem and the need to synchronise locks before the conflict can be resolved.
This paper introduces an algorithm that integrates operational transformation and multi-versioning to resolve the different types of conflict. The algorithm uses delayed post-locking to solve the partial-intention problem by making use of user intention locks. It also uses conflict tables to better facilitate the resolution of conflict as soon as possible without requiring sites to receive all operations.