ENABLE User's Guide

DEVELOPING A DATA BASE
Drawing the Relationship Between Classes of Information
DependentsEmployee
OneOne
Figure 3-4. One-to-One Relationship
After you determine the type of relationship that exists between
the classes of information, ask yourself the following questions:
• Are any of the data items associated with more than one class
of information? If so, is this duplication necessary?
• Are any of the data items repeated in the same class of data?
Depending on the answers to these questions, you might need to
draw a new diagram of the relationships between your classes of
information.
Are Data Items Associated With More Than One Class?
Some employee data (an employee number, name, branch number, and
region number) appears with both employee and dependents. To
eliminate some of this redundant information, you could remove
the employee name, branch number, and region number from the
dependents information. The employee number should remain with
both, however, so that you can form a logical connection between
these classes when you use either ENABLE or ENFORM.
Are Data Items Repeated in the Same Class of Data?
Several data items (dependent-name, relationship, and
dependent-age) can be repeated. Figure 3-5 shows some sample
data from this class of information.
3-5