Software Engineering:Chap. 6 Software Requirements

6.3 Discover the ambiguities or omissions in the following statements of the requriements for the parts of a ticket-issuing system.

An automated ticket-issuing system sells rail tickets. Users Select their desctination and input a credit card and a personal identification number. The rail ticket is issued and there credit card and a personal identification number. The rail ticket is issued and their cradit 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 trsansaction has been validated, the ticket is issued.

Ans. If a user want to buy multiple tickets,user doesn’t have option.

If user want to cancel tickets, user doesn’t have option.

Users cannot buy tickets with cash.

There was ambiguity in how potential destinations is activated.

6.6 Using the technique suggested here, where natural language is presented in a standard way, writ plausible user requirements for the following function:

♦ An unattended petrol (gas) pump system that includes a credit card reader. The customer swipes the card through the reader and then specifies the amount of fuel required. The fuel is delivered and the customers account debited.


Function: Unattended petrol pump system

Description: Validate user card by checking the card number and user pin,then approve requested amount of fuel required.

Input: Swipes credit card for account details, use numpad for specifying the amount of fuel required.

Source: Credit Card reader,numpad on system.

Output: Fuel from nozzle.

Destination: Main Control System.

Acton: Pump the gas. Compute the amount of fuel requested and deduct amount from card. If card was not valid then alert user and cancel the process.

Requires : Credit Card.

Pre condition: Credit card must be a valid one.

Post Condition : Charge the card with requested amount,fuel pumped.

Side effects : None.

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