The Scaled Agile Framework® defines Non-Functional Requirements as:
Non-functional requirements (NFRs) define system attributes such as security, reliability, performance, maintainability, scalability, and usability. They serve as constraints or restrictions on the design of the system across the different backlogs.1
For example, an organization may have standards about a specific level of accessibility compliance that apply to all digital products that the organization produces. Within this organization, a single project might have specific performance requirements on the response time of each core feature within the project. For NFR’s to be of any significant value to the organization, it requires that automated testing be implemented to validate adherence to the requirements within an environment that mirrors production.
For more information on the role of NFR’s within the context of the Scaled Agile Framework®, review the following abstract: