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SQL Triggers Reacting on Time Events: An Extension Proposal
ADBIS '09 Proceedings of the 13th East European Conference on Advances in Databases and Information Systems
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This paper proposes a simple model for a timer-driven triggering and alerting system. Such a system can be used with relational and object-relational databases systems. Timer-driven trigger systems have a number of advantages over traditional trigger systems that test trigger conditions and run trigger actions in response to update events. They are relatively easy to implement since they can be built using a middleware program that simply runs SQL statements against a DBMS. Also, they can check certain types of conditions, such as “a value did not change” or a “a value did not change by more than 10% in six months.” Such conditions may be of interest for a particular application, but cannot be checked correctly by an event-driven trigger system. Also, users may be perfectly happy being notified once a day, once a week, or even less often of certain conditions, depending on their application. Timer triggers are appropriate for these users. The semantics of timer triggers are defined here using a simple procedure. Timer triggers are meant to complement event-driven triggers, not replace them. We challenge the database research community to developed alternate algorithms and optimizations for processing timer triggers, provided that the semantics are the same as when using the simple procedure presented here.