Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

ECA Rule Condition

  • Mikael Berndtsson
  • Jonas Mellin
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_517

Definition

An ECA rule condition is either a database query, a logical expression, or a call to a subprogram (function or method) executing arbitrary code returning true or false. If database queries are employed, then a nonempty set is equivalent to true, and an empty set is equivalent to false.

Key Points

A key issue of an ECA rule condition is that it ought to take parameters carried by the event triggering the rule that, in turn, evaluates the condition. The condition either returns a set (as a result of an SQL query) or a Boolean value (as a result of evaluation of the logical expression or the execution of the subprogram). An empty set is equal to false, and a nonempty set is equal to true. Another key issue is that results of the condition evaluation can be used to optimize rule action execution in many cases. Thus, there is a need to pass parameters from the condition evaluation to the rule action execution.

Cross-References

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.University of Skövde, The Informatics Research CentreSkövdeSweden
  2. 2.University of Skövde, School of InformaticsSkövdeSweden

Section editors and affiliations

  • M. Tamer Özsu
    • 1
  1. 1.Cheriton School of Computer ScienceUniversity of WaterlooWaterlooCanada