In this blog post, we explore the topic of non-functional requirements (NFRs) and their crucial role in software development.

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1. What are non-functional requirements?

Non-functional requirements, also known as non-functional needs, differ from functional needs in that they focus on “how” a system or software should work, as opposed to “what” it should do. While functional requirements (FRs) describe the operation of a system and define its behavior, NFRs encompass how to deliver this operation. An efficient and effective application includes both FRs and NFRs, and understanding this distinction is essential to successful software development.

FRs are needed to achieve the “Fit for purpose,” while NFRs contribute to both functional operation and application performance. Without FRs, a system could not function as intended, but without NFRs, the system would not work efficiently, leading to user frustration.

2. Examples of functional and non-functional requirements

Examples of FRs and NFRs can vary depending on the nature of the project, but they can be divided into categories such as business rules, performance, security, and so on. Some examples include:

• FR: The application should provide a feedback mechanism for users.
  NFR: The confirmation screen should load within 2 seconds of pressing the ‘Send’ button.
• FR: Orders placed before 10 p.m. should be delivered the next day.
  NFR: The lead time between placing an order and informing the dispatcher should not exceed 5 minutes.

3. Responsibility for setting requirements

Collecting both FRs and NFRs is a joint responsibility, with various stakeholders contributing to the process. While FRs are often collected by analysts or product owners with input from various stakeholders, collecting NFRs requires close collaboration between business and IT. It is vital to start this process early and integrate it with the development of functional requirements to ensure successful implementation.

4. Implementation and testing of non-functional requirements.

Implementing NFRs requires a structured approach, both for new and existing applications. For existing applications, it is important to maintain a priority list of NFRs and implement them in an integrated manner. For new applications, early integration and planning is essential to ensure a smooth implementation. Testing NFRs requires specific tools and techniques to ensure compliance.

5. Take-away

Understanding and implementing both functional and non-functional requirements is essential to software development success. By integrating NFRs early in the development process and close collaboration between business and IT, organizations can build applications that not only meet functional requirements but also work efficiently and effectively for users.