What is active database? Discuss generalized mode for active databases?

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Active Databases 

 A trigger is a procedure that is automatically invoked by the DBMS in response to changes to the database and is specified by the database administrator (DBA). A database with a set of associated triggers is generally called an active database. 

Generalized Model for Active Databases 

The model that has been used to specify active database rules is referred to as the Event-Condition-Action (ECA) model. A rule in the ECA model has three components:

1. The event(s) that triggers the rule: These events are usually database update operations that are explicitly applied to the database. However, in the general model, they could also be temporal events 2 or other kinds of external events.

2. The condition that determines whether the rule action should be executed: Once the triggering event has occurred, an optional condition may be evaluated. If no condition is specified, the action will be executed once the event occurs. If a condition is specified, it is first evaluated, and only if it evaluates to true will the rule action be executed.

3. The action to be taken: The action is usually a sequence of SQL statements, but it could also be a database transaction or an external program that will be automatically executed. 






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