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Petrol Pump System Sequence

publish date: 2026/06/06 23:08:29.960477 UTC

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Consider an unattended petrol pump system. The customer swipes their credit card, specifies the amount of fuel required, fuel is delivered, and the customer's account is debited. Which of the following correctly captures this as a user requirement in standard natural language format?

The system shall only deliver premium fuel regardless of customer selection.

The customer should swipe their card at some point during the transaction.

The system shall deliver fuel to the customer after validating the credit card and receiving a fuel amount selection, and shall debit the customer's account upon completion of delivery.

The system should maybe allow the customer to select fuel if the card is present.

Correct Answer

The system shall deliver fuel to the customer after validating the credit card and receiving a fuel amount selection, and shall debit the customer's account upon completion of delivery.

Explanation

This requirement correctly uses 'shall' for mandatory behavior, describes the complete sequence (card validation → fuel selection → delivery → debit), and is written in standard natural language format without implementation details. The other options either use vague language, impose incorrect behavior, or misuse 'should' for what is clearly a mandatory requirement.

Reference

Software Engineering, Ian Sommerville, 9th edition

Quizzes you can take where this question appears

Applied Requirements Engineering - Exercises