Propagating updates efficiently in hierarchically structured data

One embodiment of the present invention provides a system that efficiently propagates changes in hierarchically organized data to remotely cached copies(118) of the data. The system operates by receiving (302) an access to the data at a client. In response to this access, the system determines (304) if the client (106) contains a copy of the data. If so, the system sends a request (308) to a server (104) for an update (122) to the copy. The server (104) receives the request and determines differences (310) between the current version of the data (116) at the server and an older copy of the data (118) at the client, which the server has stored locally. These differences are used to construct (312) an update (122)for the copy of the data, which may include node insertion and node deletion operations for hierarchically organized nudes in the data. Next, the update is sent (314) to the client (106) where it is applied to the copy of the data to produce an updated copy of the data. Finally, the original access is allowed (318) to proceed on the updated copy of the data. According to one aspect of the present invention, the act of determining differences (310), and the act of using the differences to construct (312) the update both take place during a single pass through the data. According to another aspect of the present invention, the update (122) for the copy of the data may include node copy, node move, node collapse and node splitting operations.