A functional requirement states what a feature or system must provide: its functionality, value, and user flow. It answers what should be designed, while nonfunctional requirements shape how it should work under the hood. section 2.3
Use functional requirements to frame the intended system behavior before discussing implementation constraints:
- Describe the feature’s user-visible purpose and value. section 2.3
- Separate the desired outcome from performance, security, portability, and other nonfunctional concerns. section 2.3
- Make the requirement specific enough to support risk discussions; “incorrect model prediction” alone is too vague as a risk. section 2.3
Dynamic pricing
A pricing system may need to optimize revenue, margin, or traffic, operate at user level, adapt to changing behavior, and produce prices in real time. Those intended capabilities are functional requirements; constraints and safeguards describe how the system must operate. section 2.3
