Final answer:
User interface design is not an example of a non-functional requirement; rather, it is a functional requirement that details system behavior and user interaction, unlike performance, security, and reliability, which are non-functional requirements that describe the system's quality.
Step-by-step explanation:
The student's question regards identifying which of the following is not an example of a non-functional requirement: performance, security, reliability, or user interface design. Non-functional requirements are criteria that can be used to judge the operation of a system, rather than specific behaviors, which are known as functional requirements.
The options given include performance, security, and reliability, which are indeed examples of non-functional requirements because they describe aspects of the system's quality and operation. However, user interface design is typically considered a functional requirement because it specifies how the system should behave and how users will interact with it. Therefore, user interface design is not an example of a non-functional requirement. In the context of evaluating the quality of a design, engineers focus on attributes of the product (non-functional requirements) and it's important that prototypes are tested adequately to ensure these requirements are met.