This ATM Object Diagram is an important behavioral diagram in the UML diagram for describing the system's dynamic aspects. These Activity Diagrams are frequently used in business process modeling, for example, to demonstrate how an ATM withdrawal works. Because they are modeled sequentially and concurrently, activity diagrams can also describe the steps in a use case diagram. The Activity Diagram below depicts how a Customer initiates a session at the ATM counter for the first time. To withdraw cash, the customer must first request the PIN, which the registered bank authorizes. When the bank confirms that the PIN matches the customer's bank account, the customer is permitted to withdraw funds from the account.