According to the BABOK Guide, high quality requirements have the following characteristics1:
Atomic: Each requirement addresses only one thing and can be verified independently.
Complete: Each requirement provides all the information necessary for the intended audience to understand it.
Consistent: Each requirement does not conflict with any other requirement or source of authority.
Correct: Each requirement accurately describes the needs of the stakeholders and the solution.
Feasible: Each requirement can be implemented within the constraints of the project and the environment.
Modifiable: Each requirement can be changed when necessary and the impact of the change can be assessed.
Prioritized: Each requirement has an agreed-upon level of importance or urgency relative to other requirements.
Testable: Each requirement can be verified using a defined process or method to determine whether it meets the acceptance criteria.
Unambiguous: Each requirement has only one possible interpretation and is clear and concise.
Understandable: Each requirement can be comprehended by the intended audience without any difficulty or confusion.
Among these characteristics, the one that demands that all requirements in a set or model support its overall purpose and scope is cohesive. Cohesion is the degree to which the elements of a set ormodel are logically related and focused on providing a specific and consistent outcome2. A cohesive set or model of requirements is easier to understand, maintain, and verify, as it avoids unnecessary complexity, redundancy, and inconsistency. A cohesive set or model of requirements also ensures that the requirements are aligned with the business objectives and stakeholder needs, and that they do not introduce any out-of-scope or irrelevant features or functions3. References:
1: BABOK Guide, section 4.1 Prepare for Elicitation, page 62
2: CBAP/CCBA Certified Business Analysis Study Guide, 2nd Edition, by Susan Weese and Terri Wagner, Wiley, 2011, page 153
3: The Four Attributes of High-Quality Requirements4, section Cohesion, page 1
