ￃﾠ The Sequence Diagram is one of the Modeling Language diagram. A sequence diagram shows, as parallel vertical lines, different processes or objects that live simultaneously, and as horizontal arrows, the messages exchanged between them, in the order in which they occur. This allows the specification of simple runtime scenarios in a graphical manner.
ￃﾠ We can simply saying that the sequence diagram will explain the sequence of steps to be performed to complete the execution.
Example: Restaurant System
ￃﾠ The below given diagram describes the sequences of messages of a (simple) Restaurant System. This diagram represents a Patron ordering food and wine, drinking wine then eating the food, and finally paying for the food. The dotted lines extending downwards indicate the timeline, time flows from top to bottom. The arrows represent messages (motivation) from an actor or object to other objects. For example, the Patron sends message ‘pay’ to the Cashier. Half arrows indicate asynchronous method calls.