Customizing the metamodel : Metamodel graphical editor : Creating user diagram types
  
Creating user diagram types
The User Diagram Type is used as the basis of creating your Meta Model Diagram. In each diagram that you create you need to specify User Definition Types, along with their properties, create User Symbol Types, along with their Properties. These Definition and Symbol types are then assigned to this diagram.
To create a user diagram type
1 From the Explorer, right-click the Definitions group and select New Definition or select Dictionary > New Definition.
2 Select User Diagram Type and name it.
3 Click OK.
See also
Creating user definition types