Rules System

• Only One Syntax

• Implementation Philosophy

  • Query Rewrite
  • Trigger or Record Level

Notes:

• Query Rewrite is very efficient when there are a small number of rules on any given constructed types and most rules cover the whole constructed type.
  

• Bad for large number of rules on each constructed type, each covering only a few instances, exceptions as well, cannot resolve situations when the rules are violated.

• Trigger- individual record accesses and updates, done by the executor. It is complementary to query rewrite.

• Use markers in the system catalog for triggers, rule wake-up information is placed on individual instances

• Rule System supports:

• view management

• integrity constraints

• referential integrity--collection of rules

• protection

• version control (V 2.1)