Active Database

Active Database
• An active database is a database that includes active rules, mostly in the form of
ECA rules. Active database systems enhance traditional database functionality with
powerful rule-processing capabilities, providing a uniform and efficient mechanism
for many database system applications. Among these applications are integrity
constraints, views, authorization, statistics gathering, monitoring and alerting,
knowledge-based systems, expert systems, and workflow management.
Event Condition Action (ECA) is a short-cut for referring to the structure of in
event driven architecture and database systems.
• Such a rule did traditionally consist of three parts:
• The event part specifies the signal that triggers the invocation of the rule
• The condition part is a logical test that, if satisfied or evaluates to true, causes the
action to be carried out
• The action part consists of updates or invocations on the local data
• This structure was used by the early research in active databases which started to use
the term ECA. Current state of art ECA rule engines uses a many variations on rule
structure. Also other features not considered by the early research is introduced,
such as strategies for event selection into the event part.
• In a memory-based rule engine, the condition could be some tests on local data and
actions could be updates to object attributes. In a database system, the condition
could simply be a query to the database, with the result set (if not null) being passed
to the action part for changes to the database. In either case, actions could also be
calls to external programs or remote procedures.
• Note that for database usage, updates to the database are regarded as
internal events. As a consequence, the execution of the action part of an
active rule can match the event part of the same or another active rule, thus
triggering it. The equivalent in a memory-based rule engine would be to
invoke an external method that caused an external event to trigger another
ECA rule.
• ECA rules can also be used in rule engines that use variants of the Rete
algorithm for rule processing.

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