GROUP 2: Ambiguities or omissions and non-functional requirements for the ticket-issuing system

Q1. Discover ambiguities or omissions in the following statement of

Requirements for part of a ticket-issuing system:

An automated ticket-issuing system sells rail tickets. Users select their destination and input a credit card and a personal identification number.

The rail ticket is issued and their credit card account charged. When the user

Presses the start button, a menu display of potential destinations is

activated, along with a message to the user to select a destination. Once a

destination has been selected, users are requested to input their credit card.

Its validity is checked and the user is then requested to input a personal

identifier. When the credit transaction has been validated, the ticket is

issued.

Answer:

Ambiguities and omissions include:

1. Can a customer buy several tickets for the same destination together or must

they be bought one at a time?

                                                  

2. Can customers cancel a request if a mistake has been made?

3. How should the system respond if an invalid card is input?

4. What happens if customers try to put their card in before selecting a

destination (as they would in ATM machines)?

5. Must the user press the start button again if they wish to buy another ticket

to a different destination?

6. Should the system only sell tickets between the station where the machine is

situated and direct connections or should it include all possible destinations?

7. Can customer buy multiple ticket using the same user card (discount card)?

8. Can customer change the ticket before ticket become invalid?

9. Can counter ticket provide the same ticket if the customer lost their ticket?

Q2. Write a set of non-functional requirements for the ticket-issuing system,

setting out its expected reliability and response time.

Answer:

Possible non-functional requirements for the ticket issuing system include:

1. Between 0600 and 2300 in any one day, the total system down time should

not exceed 5 minutes.

2. Between 0600 and 2300 in any one day, the recovery time after a system

failure should not exceed 2 minutes.

3. Between 2300 and 0600 in any one day, the total system down time should

not exceed 20 minutes.

4. After the customer presses a button on the machine, the display should be

updated within 0.5 seconds.

5. The ticket issuing time after credit card validation has been received should

not exceed 10 seconds.

6. When validating credit cards, the display should provide a status message

for customers indicating that activity is taking place.

7. The maximum acceptable failure rate for ticket issue requests is 1: 10000.

8. Ticket must be printed out in less than 1 second after validating credit card.

9. The time taken for receipts to be printed out should not exceed 1 second.

10. The maximum acceptable failure rate for transaction requests is 1:10000.

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