Which of the following is NOT an example of a non-functional requirement?

A non-functional requirement refers to criteria that can be used to evaluate the operation of a system, rather than specific behaviors or functions of that system. Examples of non-functional requirements often include performance, scalability, and security, as these deal with how well the system operates under various conditions and constraints.

Performance requirements define how quickly and efficiently a system must operate, including response times under certain loads. Scalability addresses the system's ability to handle growth, such as increased traffic or data volume, without degradation in performance. Security requirements focus on protecting data and ensuring that only authorized users can access certain features or data.

The data format, while it can influence how a system processes information, is primarily a technical detail about the representation of data rather than a measure of the system's operation or quality characteristics. It pertains more to functional requirements that dictate how data is structured and exchanged, rather than how the system performs overall under various conditions. Thus, it stands out as not being a non-functional requirement.