Active Database Systems for Monitoring and Surveillance

In many intelligence and security tasks it is necessary to monitor data in database in order to detect certain events or changes. Currently, database systems offer triggers to provide active capabilities. Most triggers, however, are based on the Event-Condition-Action paradigm, which can express only very primitive events. In this paper we propose an extension of traditional triggers in which the Event is a complex situation expressed by a Select-Project-Join-GroupBy SQL query, and the trigger can be programmed to look for changes in the situation defined. Moreover, the trigger can be directed to check for changes on a periodic basis. After proposing a language to define changes, we sketch an implementation, based on the idea of incremental view maintenance, to support efficiently our extended triggers.