External Reference
An External reference is an element that models a place, entity, or an org unit that is outside the boundaries of the system being modeled. External references are used to define a source or receiver of the arrow that goes outside the model frame.
The shape of an external reference on a diagram is a square (see Figure 1).
To add an external reference to a diagram, select it from the External References repository (Main Menu → Repositories → External References) and drag the selected item to the diagram. Or use the button from the Elements Palette of the diagram.
The same external link can be added multiple times to the same diagram. Only one incoming or one outgoing arrow can be attached to the external reference.
It is recommended to relate the external reference with the external org unit in case they model the same entity. Use the Org units tab in the External reference Properties Window to do this.