In the tree view, double-click click the icon representing the sequence diagram to which you want to add transition times.
The drawing page with the sequence diagram appears.
On the toolbar, select the Text tool .
On the drawing page, click where you want to add the name of the message instance, which represents the time the message is sent, and then type the name.
Usually, the name appears in the left margin of the diagram aligned with the message to which it applies. The name can be a simple letter, such as a or b.
On the toolbar, select the Pointer tool .
Drag a Constraint shape onto the drawing page near the message name. Double-click the shape, and under Body, type any constraint information relevant to the message time (for example, b - a < 1 sec). Click OK.
Tip: If the delivery of a message is not instantaneous, slant the message line and name the time the message is received with the same letter as the time the message is sent, but add a prime (for example, a for the time sent and a‘ for the time received).
A sequence diagram with named times for when messages are sent and received.