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Abstract

A method of monitoring objects in a database system. A client program requests monitoring of an attribute of an object in the database according to a criterion which is any of four tuning parameters. The parameters include a change value parameter, a delay time parameter, a synchronous initiation parameter, and a nervousness parameter. When an update is committed, a tracking application of a client which has requested monitoring of an attribute is invoked if the monitoring criterion specified by that client has been satisfied. The first three parameters have the effect of reducing the reactivity of the monitor. The change value parameter is satisfied if the value of the monitored attribute has changed by an amount not less than the specified change value. The delay time parameter is satisfied if at least the specified delay time has elapsed since the occurrence of a specified previous event. The synchronous initiation parameter requires that the commit be delayed until the tracker has been invoked by the notification; this parameter is satisfied by any change in value of the monitored attribute or by any of the other parameters if specified. The nervousness parameter, which increases the reactivity, is satisfied if a screening test, typically whether there has been a write to a specified relation or part of a relation, is satisfied.

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