Use Case Diagram for the ATM System

Let’s build the use case diagram of the ATM and understand the relationship between its different components.

First, we’ll define the different elements of our ATM design, followed by the complete use case diagram of the system.

System

Our system is an "ATM."

Actors

Let’s define the main actors of our ATM system.

Primary actors

Cardholder: This is the primary actor of the ATM who inserts or removes the ATM card, performs or cancels the transaction, and changes the PIN.

Secondary actors

• Card issuer: This actor verifies the cardholder's identity, checks for sufficient funds, checks the cardholder's account transaction limit, and blocks/unblocks the cardholder's account.

• System: This actor checks for sufficient funds in the ATM, checks the ATM’s transaction limit, and verifies the cardholder's identity. This actor also returns the card and dispenses the amount and receipts.

• Operator: The operator is responsible for starting and shutting down the system. It can refill printer receipts and cash dispensers.

Use Cases

In this section, we will define the use cases for the ATM. We have listed the use cases according to their respective interactions with a particular actor.

Cardholder

• Insert card: To insert an ATM card into ATM

• Transaction: To perform an operation—balance inquiry, deposit, fund transfer, or cash withdrawal

• Change pin: To change the PIN of the ATM card

• Cancel transaction: To cancel a transaction

Card issuer

• Verifying the cardholder's identity: To validate the card and cardholder's bank account details

• Check sufficient funds in account: To check if the cardholder's bank account has more or equal funds than the fund being withdrawn or transferred

• Check account transaction limits: To check if the transaction limits of the cardholder's bank account are more or equal to the funds being withdrawn or transferred

• Block/Unblock account: To block or unblock the cardholder's bank account

System

• Verifying the cardholder's identity: To validate the card and cardholder's bank account details

• Check sufficient funds in ATM: To check if the ATM has more or equal funds than the fund being withdrawn or transferred

• Check ATM withdrawal limits: To check if the transaction limits of the ATM are more or equal to the funds being withdrawn or transferred

• Return card: To return the card after completing or canceling the transaction

• Dispense money: To dispense cash in case of cash withdrawal from an ATM

• Dispense receipt: To dispense cash after completing the transaction

Operator

• System startup/shutdown: To start and shutdown the ATM session

• Refill printer receipts: To refill the paper in the printer

• Refill cash dispenser: To refill the cash in the dispenser

Relationships

This section describes the relationships between and among actors as well as their use cases.

The “Transaction” use case has a generalization relationship with the “Balance Inquiry,” “Deposit,” “Transfer,” and “Cash withdrawal,” because a cardholder can use any of these options to perform a transaction.

Associations

The table below shows the association relationship between actors and their use cases.