Nowadays, most modern large cities have an automated travel card system (London - Oyster card, Paris - Metro Pass, New York - Metrocard) designed to reduce congestion, ticket queues and increase the incentive to use public transport. This card system allows users to transfer money to their travel card either online or at an ATM style top-up machine placed conveniently at Railway or Bus Stations which support the travel card. There are also scan points placed throughout railway and bus stations where passengers must swipe their travel card before they hop onto a train or bus and again after they alight at the end of their journey. The correct amount of credit will then be computed and deducted from their cards using the start point and end points of their journeys.
Each wall mounted Travel Card Top-up Machine (TCTM) has a magnetic stripe reader for reading a travel card and another reader for laser, debit or credit cards. A console is available to allow customers to interact with the TCTM (keyboard and display) and a Screen to display information to the customer on the progress of his/her interaction. The machine also contains a slot for depositing cash, a dispenser and printer for receipts and an external switch, operated by a security key, allowing a maintenance engineer to start or stop the machine. The machine also communicates with an external data server which stores information on all transactions.
A customer is able to make a top-up onto his/her card of any amount in multiples of £5 using either cash or a payment card. The customer will enter the amount of the top- up into the machines console, and they are then prompted to choose their payment method. If the method chosen is a payment card (Debit, Laser/Credit card), the customer is then prompted to swipe their payment card on the designated reader and then prompted to enter a valid Pin for the card. The card details are then confirmed with the bank linked to the payment card. If the method for payment is cash, they are then prompted to enter banknotes in the designated slot.
Customers can also choose to have their travel card balance and previous transactions displayed for any verified travel card. It is also possible for customers to print receipts for any previous transactions through a separate menu.
Once the amount has been paid, the customer is then prompted to swipe their travel card and the transaction is then considered complete.
When topping up with a payment card, if the card and pin do not match or are invalid, the customer must renter the pin before the transaction can continue.
When a transaction is complete, the customer is provided with a receipt which is printed out, displaying the date, time, and location of the Station, amount topped up and available balance on the travel card. If a customer chooses to print a receipt relating to a previous transaction, the same details are printed. A user can also choose to print a receipt showing details of a previous journey in which their travel card was used to provide payment. In this case the receipt will contain the date, time, and location for the beginning and end of the specified journey along with the amount charged and the id number for the customers travel card.
The TCTM also has a key-operated switch that will allow an operator or technician to start and stop the servicing of customers.
Prepare a Use Case diagram for system and expand one of the identified use cases to a full textual description.
Construct a Class Diagram, illustrating the relevant classes (attributes and operations), and their relationships (associations, inheritance) in the system.
Create an interaction diagram for the use case described.