Rules and integrity constraints

1

Rules in active databases and

integrity constraints

Rules and integrity constraints

2

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

Rules and integrity constraints

3

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

Rules and integrity constraints

4

Examples

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

Rules and integrity constraints

5

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 and integrity constraints

6

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

Rules and integrity constraints

7

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)