You can create a Type Definition through a Class Diagram or a Modeler pane.
To create a type definition through a class diagram:
1. On the Class Diagram toolbar, click the Type Definition button, and then click on the diagram in free space or within a Package.
If you click within a Package on the diagram, the Type Definition is created as a child item of that Package.
2. Type the name of the Type Definition, and then press the Enter key.
By default, Modeler creates a Type Definition of Enumeration construction. If you want to change the construction to Alias, Sequence or Array, you can do so through the Options tab of the Type Definition's property pages.
To create a type definition through a Modeler pane:
1. In a Modeler pane, locate the item that is to own the Type Definition, that is, a Package, Class, Interface, Signal or the Model.
2. Right-click the owning item.
3. Point to New, point to Typedef , and then click Alias, Array, Enumeration or Sequence.
or
Point to New , point to UML , point to Structure, point to Type Definition, and then click Alias, Array, Enumeration or Sequence.
4. Type the name of the Type Definition, and then press the Enter key.
Type Definition button, and then click on the diagram in free space or within a Package.