Non-functional requirements

Definition

Non-functional requirements refer to the criteria that define how a system operates rather than what it does. These requirements encompass attributes such as usability, performance, security, and reliability, which are essential for ensuring that the system meets user expectations and performs effectively in real-world scenarios. Understanding non-functional requirements is crucial throughout the design lifecycle and during the processes of gathering and documenting requirements, as they significantly influence user satisfaction and the overall success of a project.

5 Must Know Facts For Your Next Test

1. Non-functional requirements are often described using quality attributes that specify how a system should behave under certain conditions.
2. These requirements can be measured quantitatively or qualitatively, such as response time being less than two seconds or user satisfaction ratings being above 80%.
3. Unlike functional requirements, which outline specific features or functionalities of the system, non-functional requirements focus on the overall user experience and system performance.
4. Identifying non-functional requirements early in the design process helps avoid costly changes later, ensuring that the final product aligns with user needs and expectations.
5. Common non-functional requirements include scalability, which ensures the system can grow with user demand, and maintainability, which addresses how easily the system can be updated or modified.

Review Questions

• How do non-functional requirements impact the user-centered design lifecycle?
  • Non-functional requirements play a crucial role in the user-centered design lifecycle by ensuring that user expectations are met beyond just the functional aspects of a system. They guide designers in creating interfaces that are not only functional but also easy to use, reliable, and performant. By incorporating non-functional requirements from the outset, designers can create more satisfying experiences for users and reduce the need for extensive revisions later in the process.
• Discuss the significance of accurately eliciting non-functional requirements during documentation processes.
  • Accurately eliciting non-functional requirements during documentation processes is vital for several reasons. It helps stakeholders understand critical attributes like usability and performance that affect user experience and satisfaction. Properly documented non-functional requirements also serve as benchmarks against which the system can be evaluated during testing and development phases. This ensures that all parties involved have a clear understanding of what is needed for successful implementation.
• Evaluate how misinterpretation of non-functional requirements can affect project outcomes and suggest methods to mitigate such risks.
  • Misinterpretation of non-functional requirements can lead to significant project challenges, such as a product that performs poorly or fails to meet security standards. This not only jeopardizes user satisfaction but can also result in financial losses or reputational damage for organizations. To mitigate these risks, it's essential to involve end-users in the requirement-gathering process, utilize clear documentation practices, and conduct regular reviews throughout development. Engaging in iterative testing based on defined non-functional criteria can also help catch issues early on.

Related terms

Usability:

Usability refers to how easy and intuitive it is for users to interact with a system, encompassing aspects like user interface design, accessibility, and learnability.

Performance: Performance relates to the responsiveness, speed, and efficiency of a system, determining how well it can handle user requests and data processing under various conditions.

Security: Security involves the measures taken to protect a system from unauthorized access, ensuring that user data and interactions remain confidential and secure.