A method, system, computer system, and computer program product to support a distributed environment in which changes to data shared by multiple nodes are logged using private logs and managed by a coordinator. The coordinator recognizes invalidating operations and informs a reader when data need to be read again after an invalidating operation corrupted and/or caused the copy of the data read by the reader to be out-of-date. The coordinator can provide a location from which current valid data can be read. The coordinator can use an operations history to detect invalidating operations and operations trackers to determine when a node is not synchronized with the coordinator.

 
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> Methods and architecture for cross-device activity monitoring, reasoning, and visualization for providing status and forecasts of a users' presence and availability

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