You can create inner classifiers in a class or interface.
Open the Inner Classifiers tab in the property sheet of a class or interface, and click the Add inner class or Add inner interface tool.
Right-click a class or interface in the Browser, and select or .
Select the Inner Link tool in the Toolbox and click and use it to connect two classes in the diagram. The first class will become a composite class and the second, an inner classifier
Create a composite classifier diagram dedicated to the class (see following section), and create classes or interfaces there.
All inner classifiers are listed in the bottom of the class symbol.