Writeback in the DAS Architecture. Extension of the DAS architecture for the writeback. A third party writeback server is the last to be queried by the client, and its response is used to update the information provided by the annotation servers. Communication with the writeback server has the peculiarity that the amount of information sent by the client is considerably larger than for any other server. The clock in the background represents the chronological order of the actions in a DAS transaction.