Non-functional requirements

Definition

Non-functional requirements are specifications that define the quality attributes, system performance, and constraints of a system rather than the specific behaviors or functions it must perform. These requirements focus on how a system operates, encompassing aspects such as reliability, scalability, usability, and security. They play a crucial role in shaping user satisfaction and overall system effectiveness, influencing how functional requirements are designed and implemented.

5 Must Know Facts For Your Next Test

1. Non-functional requirements can significantly impact user experience and satisfaction, as they set the expectations for how well the system should perform.
2. They are often categorized into various types such as performance requirements, security requirements, and usability requirements.
3. Non-functional requirements must be measurable to allow for effective validation and verification processes during development.
4. In model-based systems engineering, non-functional requirements are crucial for assessing trade-offs between different design alternatives and ensuring system feasibility.
5. Ignoring non-functional requirements can lead to system failures, poor user acceptance, and costly rework in later stages of development.

Review Questions

• How do non-functional requirements influence the overall design and development of a system?
  • Non-functional requirements significantly influence the overall design by providing benchmarks for quality attributes such as performance, usability, and security. These benchmarks guide the design choices made during development to ensure that the final product not only meets its functional goals but also satisfies users' expectations for how well it operates. Additionally, they help identify potential trade-offs between different design options to optimize both functionality and performance.
• Discuss the importance of measuring non-functional requirements in the context of verification and validation.
  • Measuring non-functional requirements is essential for effective verification and validation because it allows teams to assess whether the system meets its defined quality attributes. For instance, performance metrics can be used to validate speed and responsiveness under various loads. By establishing clear criteria for non-functional aspects, teams can ensure that any discrepancies are addressed early on, ultimately leading to a more reliable and acceptable final product.
• Evaluate the challenges faced in capturing non-functional requirements using models and suggest potential solutions.
  • Capturing non-functional requirements using models presents challenges such as ambiguity in definitions, difficulty in quantifying subjective criteria like usability, and the complexity of integrating these requirements with functional ones. To address these challenges, it is beneficial to use standardized frameworks for defining non-functional criteria that emphasize clarity and measurability. Incorporating stakeholder feedback early in the modeling process can also help refine these requirements, ensuring they accurately reflect user needs while remaining feasible within system constraints.

Related terms

Functional requirements: Specifications that describe the specific behaviors or functions of a system, detailing what the system should do.

Quality attributes: Characteristics that define the overall performance and user experience of a system, including reliability, availability, and maintainability.

System constraints: Limitations or restrictions placed on the design and implementation of a system, often derived from non-functional requirements.