UML Association Class
An association class models the attributes and operations of the association. It is depicted as a standard UML class connected with a dashed-lined link to the association.
How to Add Association Class
You can add an association class to the association using the context bar. Select the desired association in diagram editor and click on the Add Association Class button in the context bar. The association class connected to the association will be inserted into the diagram.
Example of Association Class
Let's have two entities - Student and Course. There is an association that represents student participation in the course. The Participation association needs other attributes such as course enrollment date and the flag for recording whether the fee was paid. These attributes will be stored in the association class.