Learning UML

Generalizations, Realizations, and Dependencies

While it is common to use types during analysis activities, interfaces during analysis activities and design activities, undifferentiated classes during design activities, and implementation classes during the later part of design and during implementation activities, how are all these elements related? Generalizations, realizations, and dependencies, called specialized relationships, address the question of how undifferentiated and differentiated classes are related. The next few sections discuss these relationships.

Generalizations

A generalization between a more general element and a more specific element of the same kind indicates that the more specific element receives the attributes, associations and other relationships, operations, and methods from the more general element. The two elements must be of the same kind. For example, a generalization relationship can be between two types but not between a type and an interface. Generalization relationships may exist for the following kinds of elements:

• Types

• Undifferentiated classes

• Implementation classes

• Interfaces

A generalization is shown as a solid-line path from the more specific element to the more general element, with a large hollow triangle at the end of the path connected to the more general element. You’ll see examples of this as I discuss each specific type of generalization in the following sections.

Types

The project manager, human resource, and system administrator types ...