9. You have been asked to take part in a checklist-based review of the following excerpt from the requirements specification for a library system:
Librarians can:
1. Register new borrowers
2. Return books from borrowers
3. Accept fines from borrowers
4. Add new books to the system with their ISBN, author and title
5. Remove books from the system
6. Get system responses within 5 seconds
Borrowers can:
7. Borrow a maximum of 3 books at one time
8. View the history of books they have borrowed/reserved
9. Be fined for failing to return a book within 3 weeks
10. Get system responses within 3 seconds
11. Borrow a book at no cost for a maximum of 4 weeks
12. Reserve books (if they are on-loan)
All users (librarians and borrowers):
13. Can search for books by ISBN, author, or title
14. Can browse the system catalogue
15. The system shall respond to user requests within 3 seconds
16. The user interface shall be easy-to-use
You have been assigned the checklist entry that requires you to review the specification for inconsistencies between individual requirements (i.e., conflicts between requirements).
Which of the following CORRECTLY identifies inconsistencies between pairs of requirements?
Explanation / Rationale
Considering the potential inconsistencies:
• 6-10 – If librarians should get system responses within 5 seconds, it is NOT inconsistent for borrowers to get system responses within 3 seconds.
• 6-15 - If librarians should get system responses within 5 seconds, it is inconsistent for all users to get system responses within 3 seconds.
• 7-12 – If borrowers can borrow a maximum of 3 books at one time it is NOT inconsistent for them to also reserve books (if they are on-loan).
• 9-11 – If a borrower can be fined for failing to return a book within 3 weeks it is inconsistent for them to also be allowed to borrow a book at no cost for a maximum of 4 weeks – as the length of valid loans are different.
Of the potential inconsistencies, 6-15 and 9-11 are valid inconsistencies.
Thus:
a) Is not correct
b) Is correct
c) Is not correct
d) Is not correct