Databases Reference
In-Depth Information
the DBMSs of the 1980s, programs were responsible for the verification of
constraints (until the 1990s relational products did not support, e.g., refer-
ential integrity or check constraints). Later, with the improvement of the
performance-to-cost ratio and optimizers, products incorporated more and
more information on constraints in the DBMS catalog, becoming semantic
DBs. In the early 1990s, active DBs appeared (see Chapter 3). In those
DBMSs, besides the description of the data and the constraints, part of the
control information is stored in the DB. Active DBs can run applications
without the users intervention by supporting triggers, rules, alerts, daemons,
and so on.
Finally, we are witnessing the appearance of object-oriented (see
Chapter 7) and object-relational (see Chapter 6) DBMSs, which allow the
definition and management of objects (encapsulating structure and behav-
ior). Objects stored in DBs can be of any type: images, audio, video, and so
on. Then, there are multimedia DBs (see Chapter 8), which could be the last
step in the evolution of DBs along the functionality dimension (Figure 1.4).
Prog. A
Prog. B
Prog. C
Prog. A
Prog. B
Prog. C
Process information
Control information
Process information
Control information
DB
DB
Constraints information
Control information
Constraints information
Data information
Data
Data information
Data
Semantic databases
Active databases
Prog. A
Prog. B
Prog. C
Process information
Control information
DB
Process information
Control information
Constraints information
Data information
Data
Object databases
Figure 1.4
Semantic, active, and object DB systems.
