Patent ID: 7340502

Claim:
Apparatus for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in deltas to each other in order to update the local data copies, the apparatus comprising: a persistent delta log data structure located in each endpoint that stores deltas and their contents; a mechanism in each endpoint that inserts each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception; and a mechanism in each endpoint that executes the data change commands in a delta on the local data copy, the mechanism, in response to an indication of non-compliance, using the contents of the delta log to selectively undo a portion of the data change commands on the local data copy, determine a reordering of the portion of the data change commands, and redo on the local data copy the portion of the data change commands as reordered to achieve convergence of the data change commands at all endpoints without user intervention.