Lecture Outline Monday 23 rd February (Week 4) 3 – 3:10pm Review of Requirements Eng. and use cases 3:10 – 3:40pm Exercise on Use Case 3:40-4:40 Class Diagrams basics

ATM –Distribute money to card holders who have a card via ATM machine –Provide information on balance if customer of bank –Allow deposits of cash and cheques if customer of bank –Is maintained by an operator who empties/refills the machine –There are security requirements performed by external systems i.e. the bank system and the VISA system Exercise 1 –Who are the actors?

Exercise 1 - solution Card holder Bank Customer Maintenance operator Bank Information System VISA Auth. system

Exercise 2 What are the use cases (ignore secondary actors – those that do nothing with the system)? SOLUTION –Cardholder Withdraw money –(Actually - Withdraw Money with bank card + Withdraw Money with VISA card) –Bank Customer Obtain balance Deposit cash Deposit Cheques –Maintenance Operator Refill dispenser Retrieve Cheques Retrieve swallowed cards

Exercise 3 – draw a use case diagram

Exercise 4 Write a description of the use case “Withdraw Money using VISA” –Objective Allow the visa customer to withdraw cash up to their limit –Preconditions In operation

Main Flow 1.Customer inserts card 2.ATM checks if card is a VISA card 3.ATM asks for PIN 4.Visa cardholder enters PIN 5.ATM checks the entered PIN against the smartchip PIN 6.ATM checks with the VISA system for authorisation 7.VISA system returns the authorisation with the withdrawal limit 8.ATM asks the VISA cardholder withdrawal amount 9.VISA cardholder enters withdrawal amount 10.ATM checks the withdrawal amount vs. limit 11.ATM asks is a receipt is required 12.VISA cardholder chooses “yes” 13.ATM returns the card 14.VISA cardholder removes card 15.ATM issues amount of cash requested plus receipt 16.VISA cardholder takes cash and receipt

Post-condition –VISA cardholder account is debited by the amount withdrawn –Cash in ATM reduced by amount withdrawn

Alternate Flows –At 2, if the card is not a VISA car: ATM displays message warning of wrong card ATM returns card to VISA cardholder VISA cardholder removes card