Event condition action (ECA) is a short-cut for referring to the structure of active rules in
event driven architecture Event-driven architecture (EDA) is a software architecture paradigm promoting the production, detection, consumption of, and reaction to events.
Overview
An ''event'' can be defined as "a significant change in state". For example, when a consumer p ...
and
active database
An active database is a database that includes an event-driven architecture (often in the form of ECA rules) which can respond to conditions both inside and outside the database. Possible uses include security monitoring, alerting, statistics gat ...
systems.
Such a rule traditionally consisted 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 the art ECA rule engines use 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
A business rules engine is a software system that executes one or more business rules in a runtime production environment. The rules might come from legal regulation ("An employee can be fired for any reason or no reason but not for an illegal rea ...
, 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
A business rules engine is a software system that executes one or more business rules in a runtime production environment. The rules might come from legal regulation ("An employee can be fired for any reason or no reason but not for an illegal rea ...
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 engine
A business rules engine is a software system that executes one or more business rules in a runtime production environment. The rules might come from legal regulation ("An employee can be fired for any reason or no reason but not for an illegal rea ...
s that use variants of the
Rete algorithm
The Rete algorithm ( , , rarely , ) is a pattern matching algorithm for implementing rule-based systems. The algorithm was developed to efficiently apply many rules or patterns to many objects, or facts, in a knowledge base. It is used to deter ...
for rule processing.
ECA rule engines
*
Rulecore
*Concurrent Rules
*Apart Database
*Detect Invocation Rules
*
ConceptBase
ConceptBase (a.k.a. ConceptBase.cc) is a deductive and object-oriented database management system developed at University of Aachen and University of Skövde. It is mainly used for conceptual modeling and metamodeling in the domain of software engi ...
ECArules
References
*Klaus R. Dittrich, Stella Gatziu, Andreas Geppert: The Active Database Management System Manifesto: A Rulebase of ADBMS Features. Lecture Notes in Computer Science 985, Springer 1995, , pages 3–20.
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Databases
Rule engines