Overview

Object-oriented (OO) approaches for software development have become extremely popular in recent years. Much of the new development is now being done using OO techniques and languages. There are many advantages that OO systems offer. An OO model closely represents the problem domain, which makes it easier to produce and understand designs. As requirements change, the objects in a system are less immune to these changes, thereby permitting changes more easily. Inheritance and close association of objects in design to problem domain entities encourage more reuse, that is, new applications can use existing modules more effectively, thereby reducing development cost and cycle time. Object-oriented approaches are believed to be more natural and provide richer structures for thinking and abstraction. Common design patterns have also been uncovered that allow reusability at a higher level. (Design patterns is an advanced topic which we will not discuss further; interested readers are referred to [69].)

The object-oriented design approach is fundamentally different from the function-oriented design approaches primarily due to the different abstraction that is used. It requires a different way of thinking and partitioning. It can be said that thinking in object-oriented terms is most important for producing truly object-oriented designs.

During design, as mentioned in the previous chapter, our focus is on what is called the module view in architecture. That is, the goal is to identify the modules that the system should have, and their interfaces and relationships. In OOD, we are therefore identifying the classes that should exist in...