Notes

4.1. Identify and briefly describe four types of requirements that may be defined for a computerbased system.
4.2. Discover ambiguities or omissions in the following statement of the requirements for part of a drone system intended for search and recovery: The drone, a quad chopper, will be very useful in search and recovery operations, especially in remote areas or in extreme weather conditions. It will click high-resolution images. It will fly according to a path preset by a ground operator, but will be able to avoid obstacles on its own, returning to its original path whenever possible. The drone will also be able to identify various objects and match them to the target it is looking for.
4.3. Rewrite the above description using the structured approach described in this chapter. Resolve the identified ambiguities in a sensible way.
4.4. Write a set of non-functional requirements for the drone system, setting out its expected safety and response time.
4.5. Using the technique suggested here, where natural language descriptions are presented in a standard format, write plausible user requirements for the following functions: An unattended petrol (gas) pump system that includes a credit card reader. The customer swipes the card through the reader, then specifies the amount of fuel required. The fuel is delivered and the customer’s account debited. The cash-dispensing function in a bank ATM. In an Internet banking system, a facility that allows customers to transfer funds from one account held with the bank to another account with the same bank.
4.6. Suggest how an engineer responsible for drawing up a system requirements specification might keep track of the relationships between functional and non-functional requirements.
4.7. Using your knowledge of how an ATM is used, develop a set of use cases that could serve as a basis for understanding the requirements for an ATM system.
4.8. To minimize mistakes during a requirements review, an organization decides to allocate two scribes to document the review session. Explain how this can be done.
4.9. When emergency changes have to be made to systems, the system software may have to be modified before changes to the requirements have been approved. Suggest a model of a process for making these modifications that will ensure that the requirements document and the system implementation do not become inconsistent.
4.10. You have taken a job with a software user who has contracted your previous employer to develop a system for them. You discover that your company’s interpretation of the requirements is different from the interpretation taken by your previous employer. Discuss what you should do in such a situation. You know that the costs to your current employer will increase if the ambiguities are not resolved. However, you also have a responsibility of confidentiality to your previous employer.