TRENDS IN DATABASE TECHNOLOGY - Database Design and Development: An Essential Guide for IT Professionals - page 664

Rules are stored in the database itself. The programs or modules to be executed
on the occurrence of the events are also stored in the database. The programs are
generally known as triggers or trigger programs. In relational databases, triggers are
specialized versions of stored procedures.
Here are a few considerations for designing triggers:

• Ensure that a trigger does not create a chain reaction of triggers.
• Set priority for actions if several actions are possible for the same event.
• Depending on the nature of a particular event, set the trigger to start
executing as soon as an event is sensed or immediately after an event
completes.
• Address runtime errors that may result from the execution of a trigger.

Intelligent Databases

In the evolution of database systems, as of now, intelligent databases are perhaps
the culmination of the search for better methods of storage and access of data.
Intelligent databases provide a natural way to use them; they handle seamless
movements of huge data volumes; they provide an appropriate set of user tools.
Intelligent database systems integrate sophisticated technologies such as object ori-
entation, hypermedia, expert systems, text-based searches, and online information
retrieval with database technology.
Intelligent databases offer services at three levels: database engine at the foun-
dational level, user interface at the middle level, and tools at the highest level. Figure
20-24 presents the architecture at these three levels.

Knowledge Discovery
Decision Support
Systems Decision
Quality Control
Data Integrity
Presentation Personal Databases

Navigation Tools
Semantic Editing
Object Editing
Note Taking
Multimedia

Transaction Manager
Explanation Manager
Multimedia Manager
Metadata Manager
Database Compiler
Inference Engine
Rule Manager

Tools

User Interface

Database Engine

Figure 20-24 Intelligent database architecture.