• Evolution of the Use-Case Model

Step-­by-­step outline

1. Insert Card
2. Validate card
3. Enter pin
4. Select withdraw
5. Select account
6. Select amount
7. Send transaction
8. Receive ok
9. Dispense money
10. Print receipt
11. Eject card

List of Alternative flows

A1 Wrong PIN
A2 No money
A3 Attempt to withdraw more than daily amount
A4 No contact
A5 Link goes down ­
      i)  If the link goes down before the transaction reaches the actual account. ­ Not a big problem.
     ii) ­ If the transaction reaches the account and then the link is down. The money is withdrawn but never dispensed! ­ Do we        need some kind of two­ phase­ commit?
A6 Stolen card
A7 Out of money