Offline data is easy enough, something like sqlite with the right synchronization will do the job. Writes are harder, you need to capture user actions at a fair

Offline data is easy enough, something like sqlite with the right synchronization will do the job. Writes are harder, you need to capture user actions at a fairly coarse level and be able to replay them on the server when a connection is available. These actions need to be treated as facts that have happened and not fail because of some sort of validation that can only be done on the master version. General guidance for enterprise architecture will be of benefit, it's very similar to having multiple systems synchronized via an ESB.