What is one of the difficulties with determining acceptance criteria for non-functional requirements?

Determining acceptance criteria for non-functional requirements often presents challenges due to the sometimes ambiguous nature of these requirements. Non-functional requirements, such as performance, security, and usability, are not always explicitly stated and may be assumed to be understood by stakeholders. This lack of clarity can lead to difficulties in creating specific, measurable criteria against which acceptance can be judged.

When non-functional requirements are vaguely defined, it becomes challenging to establish clear metrics for acceptance. For example, statements like "the system should be fast" do not provide a concrete threshold that can be measured or validated. Therefore, the difficulty lies in the fact that without precise specifications, it is hard to determine if the requirements have been met, potentially leading to disagreements or misunderstandings between stakeholders and developers.

Other options present solutions or issues that do not align with the nature of non-functional requirements. The perception that non-functional requirements are only considered when they are missing overlooks the proactive aspects of requirements gathering. The notion that acceptance criteria cannot be defined at all is not entirely accurate, as it is certainly possible to define these criteria, but it requires more effort and collaboration. Lastly, while end users play a significant role in defining acceptable non-functional attributes, it is not solely their responsibility, as developers and other