Sequence Diagrams

Sequence diagrams emphasize the time ordering of messages between objects. Sequence diagrams are used to model the dynamic aspects of a system. These diagrams use concrete instances of classes, interfaces and components along with the messages dispached among them in the framework of a scenario that illustrates a behavior. Interaction diagrams are useful in understanding how a particular society of objects behave over time.
 

Figure 1 - Example Sequence Diagram