System for sending small positive data notification messages over a network to indicate that a recipient node should obtain a particular version of a particular data item

摘要

A system is provided for eliminating time-consuming, unnecessary transfersf data over networks such as the the World Wide Web while at the same time guaranteeing timeliness of the data used by recipients. Timeliness is assured by immediately sending small data- notification messages whenever data becomes relevant or changes. Efficiency is guaranteed by transmitting the data itself only when requested by the recipient of a data-notification message. In particular, recipients are alerted to the presence of, and changes in, data they might use by data- notification messages containing a timestamp, the data location, and a checksum. Based on the timestamp, the recipient can determine whether the data-notification message contains timely information or should be ignored. Based on the data location and checksum, the recipient can determine whether it already has the current version of the data in question, for example stored in a cache.