Database and Expert Systems Integration - Information Systems Reengineering, Integration and Normalization - page 316

Persons

Male Female

Generalization

Fig. 8.7 The static hierarchy structure

The method of salary_refuse is that no raise more than 500 is allowed. (Note: sal-
ary@new is the data for new salary.)

If salary@new - alary>500
Then (fail)

8.2.1 The Hierarchical Structure

The frame model metadata uses the generalization relationship to build its hierar-
chical structure. There are three different types in the frame model metadata, i.e.,
static generalization, active generalization, and coupling generalization. These are
discussed below.

1. Static Generalization

Static objects use the generalization relationship to represent abstract knowledge in
their hierarchical structure. For example, we can use a static hierarchical structure
to represent Male person knowledge by creating a new class called Male as shown
in Fig. 8.7 . The new class Male inherits all the features of the Persons class and ap-
pends with it a constraint rule to ensure that the sex of the person is male. This type
of generalization can be found in most semantic data models.

2. Active Generalization

Active classes use the generalization relationship to represent the hierarchical rule
structure that is found in most production rule systems. This enables the system to
represent complex knowledge. This also enables the system to easily trigger rules,
since all related rules are clustered together, i.e., stored in the same object because
of inheritance. For example, consider the family rule base system shown in Fig. 8.8 .
This rule base is presented in a format devised by the author.
Each rule is represented as an active class as shown in Fig. 8.9 . The Son class
inherits all the attributes and methods from the Male class and the Child class. The
system will easily trigger the child rule (i.e., method child) and the male rule (i.e.,