Asynchronous reconciliation based on operational transformation for P2P collaborative environments

Reconciling divergent copies is a problem encountered in distributed systems, groupware, version control systems and personal work involving several mobile computing devices. Published reconciliation methods, whether synchronous or asynchronous, require some ordering facility provided either by a central component (master copy, sequencer) or by a fully distributed mechanism (timestamps, state vectors,...). Nevertheless, scalability is limited. This paper presents an asynchronous algorithm based on Operational Transformations which provides the means to reconcile any number of copies, without this limitation. Copies can be modified (concurrently or not) and then reconciled pair-wise, at any time, regardless of the pair, while their convergence is achieved. Its main advantage is thus to enable free propagation of update operations while ensuring they will be ordered in the same global order.