Identifying Functional Requirements

Functional requirements specify the behaviors and functions the system must perform. They define what the system should do. Examples include specific user actions, data processing, and system outputs.

Non-functional requirements, in contrast, define the qualities or constraints of the system, describing how the system should operate. These include performance, security, usability, and reliability.

Analysis of Options

• Option 1: "The system should respond within 3 seconds for 90% of user queries." This describes the system's performance, which is a non-functional requirement.

• Option 2: "The system must be available 99.9% of the time." This relates to the system's availability, a non-functional requirement.

• Option 3: "The system should be easy to learn and use." This addresses the system's usability, which is a non-functional requirement.

• Option 4: "The system shall allow users to search for products by category." This defines a specific function the system must provide—searching for products. Therefore, it is a functional requirement.

Conclusion

The requirement that describes a specific action or capability of the system is the functional requirement. Option 4 clearly outlines a function the system must perform.