Design Patterns Explained: A New Perspective on Object-Oriented Design

What Is the UML?

The UML is a visual language (meaning a drawing notation with semantics) used to create models of programs. By models of programs, I mean a diagrammatic representation of the programs in which one can see the relationships between the objects in the code.

The UML has several different diagrams—some for analysis, others for design, and still others for implementation (or more accurately, for the dissemination, that is, the distribution of the code) (see Table 2-1). Each diagram shows the relationships among the different sets of entities, depending upon the purpose of the diagram.

Table 2-1. UML Diagrams and Their Purposes

When You Are…	Use the UML Diagram…
In the analysis phase	Use Case Diagrams, which involve entities interacting ...