Rules in active databases and integrity constraints

Recap integrity constraints normal forms express FDs, MVDs, JDs candidate and foreign keys entity integrity referential integrity; foreign key rules business (enterprise) integrity constraint rules domain constraints attribute constraints relation constraints database constraints

Integrity constraints - issues declarative do not specify when to be applied and what action to take in case of violation, because they are known by default application NF, attribute and relation constraints and CK - instantaneously database constraints and FK - deferred until end of transaction action relation constraints and CK - reject database constraints - ROLLBACK transaction FK - FK rules

Examples provide examples of integrity constraints and consider the two issues application reaction to violation

Recap rules in active databases general model event condition action in the rest of this lecture rules are considered only from the point of view of enforcing integrity constraints

Rules in active databases - issues procedural specify when to be checked what event (UPDATE, DELETE, INSERT) on which object specify the action to be taken

Activity (possible topic for the last coursework) compare, from the point of view of integrity constraint enforcement: normal forms keys (candidate and foreign) domain, attribute, relation and database constraints (conditional expressions written explicitly) rules (from active databases)