3.1. UML Class Diagram
The UML class diagram shows the static structural behavior of the system, in which attributes
and operations are designed for the complete system. The classes can be related to each other in
number of ways, like they can be associated, dependent, specialized or packaged. A system can
have a number of class diagrams because not all classes participate in a single class diagram.
Figure 1 presents the class diagram of the post office system. The class diagram has eight
persistent classes, which are Person, Address, Customer, Postal_wrkr, Postal_Agent,
Schm_Invnt, Scheme, Sales_Report and one transient class Control. These classes are connected
to each other by various relationships with their multiplicities as shown in the diagram and the
Control class is used to manage all persistent classes. Customer, Postal_wrkr and Postal_Agent
are inherited from non-abstract class Person.