Propogating updates efficiently in hierarchically structured data under a push model

Abstract

One embodiment of the present invention provides a system that efficiently propagates changes in hierarchically organized data to remotely cached copies of the data. The system operates by receiving changes to the data located on the server, and applying the changes to the data on the server. These changes are propagated to remotely cached copies of the data on a client in response to an event on a server, and independently of events on the client, by (1) determining differences between the current version of the data at the server and an older copy of the data at the client, which the server has stored locally; (2) using the differences to construct an update for the copy of the data, which may include node insertion and node deletion operations for hierarchically organized nodes in the data; and (3) sending the update to the client where the update is applied to the copy of the data to produce an updated copy of the data. According to one aspect of the present invention, the act of determining differences, and the act of using the differences to construct the update both take place during a single pass through the data. According to another aspect of the present invention, the update for the copy of the data may include node copy, node move, node collapse, node split, node swap and node update operations.