Example of a sequence diagram

The following example shows a sequence diagram taken from the PiggyBank sample that is available in the Samples Gallery, which describes the DisplayBalance use case from an online banking scenario.
The sequence diagram shows the sequence of actions that occur when customers view the balance of their bank accounts.

There are four participants in the interaction between the customers and the online banking system: Customer, MenuForm, DisplayBalanceForm, and Account. Each participant is represented by a lifeline in the interaction frame.

Each action that occurs between the lifelines is represented by a message and the messages are in a specific, numbered sequence.