Non-functional requirements

Definition

Non-functional requirements are specifications that define the quality attributes, system performance, usability, and constraints of a system, rather than the specific behaviors or functions it must perform. These requirements are crucial for understanding how a system will operate in various conditions and are essential in ensuring user satisfaction and system reliability.

5 Must Know Facts For Your Next Test

1. Non-functional requirements often include criteria such as security, reliability, maintainability, and portability, all of which contribute to the overall quality of the system.
2. Unlike functional requirements that specify what the system should do, non-functional requirements focus on how the system performs its tasks.
3. Non-functional requirements can significantly impact the architecture and design choices made during development, as they often dictate technology selection and system structure.
4. Measuring non-functional requirements can be challenging since they often require specific metrics and testing methods to evaluate success or failure.
5. Addressing non-functional requirements early in the development process can prevent costly rework later on, as they are vital for ensuring that the final product meets user expectations.

Review Questions

• How do non-functional requirements influence the design decisions made during system development?
  • Non-functional requirements play a critical role in shaping design decisions by establishing the standards that the system must meet regarding performance, security, and usability. For instance, if a non-functional requirement specifies that a system must handle 10,000 concurrent users, this requirement will directly influence choices about server architecture and load balancing strategies. Designers must prioritize these requirements to ensure that the end product not only functions correctly but also performs well under expected conditions.
• Discuss the relationship between non-functional requirements and user satisfaction in embedded systems.
  • Non-functional requirements are closely tied to user satisfaction because they define how well a system operates from the user's perspective. For example, if an embedded system has high usability and quick response times but fails to meet performance benchmarks, users may become frustrated despite its functional capabilities. Therefore, balancing both functional and non-functional requirements is crucial in delivering a product that not only meets technical specifications but also delights users through reliable and efficient operation.
• Evaluate the challenges involved in defining and measuring non-functional requirements in an embedded systems context.
  • Defining and measuring non-functional requirements in embedded systems can be quite challenging due to their subjective nature and the need for specific metrics. Unlike functional requirements that can be tested through specific use cases, non-functional aspects like security or usability require comprehensive testing strategies that may involve user feedback and performance benchmarking. This complexity necessitates careful consideration during the planning phase to ensure adequate evaluation methods are established, helping to ensure that the final product adheres to these essential quality standards.

Related terms

Performance: A measure of how efficiently a system performs its functions, often defined in terms of response time, throughput, and resource usage.

Usability:

The ease with which users can interact with a system, encompassing aspects like learnability, efficiency, and user satisfaction.

Scalability:

The ability of a system to handle increased loads or to be expanded to accommodate growth without compromising performance.