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Ticket System: Core Ambiguity

publish date: 2026/06/06 23:08:28.261606 UTC

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An automated ticket-issuing system description:

"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..."

What is the key ambiguity created by describing the process in two different sequences in the same paragraph?

b) The paragraph uses both 'personal identification number' and 'personal identifier' — it is unclear if these are the same thing

a) The paragraph contradicts itself — the first sentence says users select destination first then input a card, but the second part says pressing start activates the destination menu, which could mean the card is inserted before or after destination selection

d) Both A and B are ambiguities present in the text

c) The paragraph does not specify how many destinations are available

Correct Answer

d) Both A and B are ambiguities present in the text

Explanation

Two ambiguities exist: (1) The first sentence implies users select destination then input card, but the later description shows start button → destination menu → card input, creating inconsistency in the stated sequence. (2) 'Personal identification number' (in sentence 1) vs. 'personal identifier' (later) are different terms that may or may not refer to the same thing.

Reference

Software Engineering, Ian Sommerville, 9th edition

Quizzes you can take where this question appears

Applied Requirements Engineering - Exercises