Within a sequence diagram, an object is shown as a box at the top of a dashed vertical line (see Figure 5-1).
Figure 5-1. Sequence Diagram
This vertical line is called the object's lifeline. The lifeline represents the object's life during the interaction. This form was first popularized by Jacobson.
Each message is represented by an arrow between the lifelines of two objects. The order in which these messages occur is shown top to bottom on the page. Each message is labeled at minimum with the message name; you can also include the arguments and some control information. You can show a self-call, a message that an object ...