Adding operation messages to a sequence diagram
You can add operation messages to a Sequence Diagram through the sequence diagram tab or through a drag-and-drop operation.
To add an operation message through the sequence diagram tab:
1. On the Sequence Diagram tab, click the 
Operation button.
Operation button.2. In line with the required Statement, click the lifeline of the source object, that is, the System Boundary, a Package, an Instance, an Actor, a Part or a Port.
3. Click the lifeline of the target object, that is, a Package that owns (or is going to own) the Operation, or an Instance, Part or Port whose type owns (or is going to own) the Operation.
4. From the Selection dialog, select the required Operation, and then click OK; or click the New button.
Modeler adds an Operation message to the diagram.
5. If you want to set instance properties of the Operation message:
a. Right-click the Operation message, and then click Instance Properties.
b. On the Actual Parameters tab, specify any Actual Parameters.
c. On the Options tab, specify the Return Value, Variable Name and Latency as required.
To add an operation message through a drag-and-drop operation:
1. Open the Sequence Diagram.
2. From an appropriate pane, drag the Operation you want to add to the calling object (System Boundary, Package, Instance, Part or Port).
Modeler adds an Operation message to the diagram.
3. If you want to set instance properties of the Operation message:
a. Right-click the Operation message, and then click Instance Properties.
b. On the Actual Parameters tab, specify any Actual Parameters.
c. On the Options tab, specify the Return Value, Variable Name and Latency as required.