Data server with data probes employing predicate tests in rule statements

摘要

A data server data base system is enhanced by the inclusion of Event processing in which the occurrence of an event based on a predicate test is determined by the data server without requiring attention of the user application. In particular, the user application stores a rule statement in the data server and then references that statement by name in a data inquiry. An event level data probe is invoked to collect the data referenced in the rule statement and the collected data is tested in accordance with the rule statement to determine if the event has occurred. Data passing the rule statement test is returned to the user application if the event is determined to have occurred unless Delta processing is invoked in which case only data representing a transition from Event true to Event false or Event false to Event true is returned.