You can add properties to an association between classes or interfaces by creating an association class. It is used to further define the properties of an association by adding attributes and operations to the association.
An association class is an association that has class properties, or a class that has association properties. In the diagram, the symbol of an association class is a connection between an association and a class. Association classes must be in the same package as the parent association; you cannot use the shortcut of a class to create an association class.
The class used to create an association class cannot be reused for another association class. However, you can create other types of links to and from this class.
In the following example, the classes Student and Subject are related by an association exam. However, this association does not specify the date of the exam. You can create an association class called Exam that will indicate additional information concerning the association.
