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Why is writing requirements rationale important?

Writing requirements rationale is important because it helps to explain the reasoning behind the requirement, and why it is necessary for the project. This can help to ensure that the requirement is clear, consistent and aligned with the needs of the stakeholders. It also helps to ensure that the requirement is testable and achievable within the given constraints.

  1. Improves understanding: Writing a rationale for a requirement helps to improve the understanding of the requirement and its purpose, which can help to ensure that the requirement is clear and consistent.
  2. Facilitates decision-making: A rationale can provide important information that can help to facilitate decision-making, such as the impact of the requirement on the project, and the trade-offs involved.
  3. Provides context: A rationale can provide important context that can help to ensure that the requirement is aligned with the needs of the stakeholders, and that it is achievable within the given constraints.

Examples:

  • Example 1: A requirement for a financial software to encrypt all data stored in the system. The rationale for this requirement could be that it is necessary to protect the sensitive financial information of the customers from unauthorized access.
  • Example 2: A requirement for a mobile app to support offline mode. The rationale for this requirement could be that it is necessary to provide a seamless user experience, even when the user doesn't have internet access.
  • Example 3: A requirement for a website to be optimized for accessibility. The rationale for this requirement could be that it is necessary to ensure that the website is usable for users with disabilities.

Conversely, a use case for bad requirement could be A requirement for a website to include a scrolling marquee on the homepage. The rationale for this requirement could be that it is "cool" or "trendy" feature, however it could be considered a bad requirement because it could be considered as a distraction for the users, it could be hard to read, it may not be accessible for users with certain disabilities, and it may not align with the goals and objectives of the project. A rationale for this requirement could explain why it is not aligned with the goals and objectives of the project, how it could be harmful for the users and why it should be rejected.