Databases Reference
In-Depth Information
Active Databases
Oscar Díaz and Norman Paton
3.1
Introduction
DBMSs are at the heart of current IS technology. They provide reliable, effi-
cient, and effective mechanisms for storing and managing large volumes of
information in a multiuser environment. In recent years, there has been a
trend in DB research and practice toward increasing the proportion of the
semantics of an application that is supported within the DB system itself.
Temporal DBs, spatial DBs, multimedia DBs, and DB programming lan-
guages are examples of that trend. Active DBs can be considered part of this
trend, where the semantics that are supported reflect the reactive behavior of
the domain.
Traditional DBMSs are passive in the sense that commands are exe-
cuted by the DB (e.g., query, update, delete) as and when requested by the
user or the application program. However, some situations cannot be mod-
eled effectively by that pattern. As an example, consider a university DB
where data are stored about students, lecturers, timetables, bus schedules,
and so on and which is accessed by different terminals. As new students join
the school (i.e., a new tuple is inserted in the student table), the bus should
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