Creating an interaction with an Existing Exchange Contract
To create an interaction:
1. In the diagram objects toolbar, click Interaction 
.
.2. Draw a link between the two entities in communication.
The Add Interaction dialog box appears.
3. Click the arrow at the right of the Exchange Contract field and select Create Exchange Contract.
4. Enter the Name of your exchange.
5. Click OK to close this dialog box.
The exchange is automatically created.
6. Click OK.
The interaction appears in the diagram.