Class Diagram

Icon

The icon is of a diagram with a class in it.

Use

Class diagrams are the central diagram type of UML. They describe a system's classes, its properties, operations and relationships between classes. Class diagrams are implemented in all phases of the software development process.

Modeled contents and vocabulary used needs to be tailored towards the group of persons participating. A class diagram models a partial section of the real world. Only classes and properties which are needed for describing the problem area are taken into consideration. Differentiations are generally made between the analysis model and the design model when modeling class diagrams:

• Analysis Model

  From an analysis point of view, class diagrams show what the system should achieve from the view of the user. They map classes, attributes, operations and their relationships which should all be contained in the software system developed later from the business perspective of things.

• Design Model

  The analysis model is mapped to the implementation technology in the design model. From a design point of view, class diagrams show how the system needs to be constructed technically so that it can carry out the properties required during analysis. Structures recognized and documented within system analysis are extended to include information required to implement the business model.

Class Diagram Elements

The following model elements can be shown as nodes and edges in class diagrams:

Icon	Element	Description
	Package
	Class	A class contains the description and structure of objects which can be created using it (templates for objects). A class is defined by its attributes and operations.
	Data Type
	Enumeration Type
	Primitive Type
	Interface	An interface realizes feature use between user and provider.
	Association Class
	Attribute	An attribute is an element that appears identically in a class' object. Its type is used for limiting an attribute's value range.
	Operation	Operations realize the behavior of classes and define which types the values which are exchanged are from (parameter).
	Enumeration Literal
	Generalization	Generalizations, associations, dependencies, uses, abstractions, realizations etc. express various types of relationships between classes and describe the structure classes.
	Association
	Dependency
	Use
	Abstraction
	Realization

Example of a Class Diagram

Further Information

http://www.uml.org/