Fundamentals of UML Diagrams

A diagram is the graphical presentation of a set of elements. UML has a lot of different diagrams. Read this section, and make sure you can differentiate between different diagrams.

1. Basic Use Case Notation

1.1. A Class Diagram

In Object Oriented design and development terms, a class has a name, a set of methods (also known as operations) and related data members (also known as attributes) as shown in Figure 2.1. Class by itself is not very useful. A large software system may have thousands of classes, Modelling the relationships (association, inheritance, composition or aggregation) between them really defines systems behaviour.

Class diagrams shows a set of classes, interfaces, and collaborations and their relationships. Class diagrams are the most common diagrams found in modelling object-oriented systems. It is an essential aspect of any Object Oriented Design method. 

Class diagrams address the static design view of a system. They are used at the analysis stage as well as design. Class diagrams that include active classes address the static process view of a system. Class Diagram syntax are being used to draw a plan of the major concepts for anyone to understand. This is called the Conceptual Model. Together with use cases, a conceptual diagram is a powerful technique in requirements analysis. Figure 2.2 shows an example of a class diagram.

Figure 2.2: An Example of a Class Diagram2.2.3