Last updated on Sep 15, 2024

How do you deal with non-functional system requirements such as security, performance, and usability?

Non-functional system requirements (NFRs) are the qualities or constraints that affect how a system works, rather than what it does. They include aspects such as security, performance, usability, reliability, scalability, and maintainability. NFRs are often overlooked or neglected in the requirements engineering process, but they can have a significant impact on the success and satisfaction of the system stakeholders. How do you deal with NFRs effectively and efficiently? Here are some tips and best practices to help you.

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1 Identify and prioritize NFRs

The first step is to identify and prioritize the NFRs that are relevant and important for your system. You can use various sources of information, such as stakeholder interviews, surveys, standards, regulations, benchmarks, and competitors. You can also use techniques such as brainstorming, scenarios, use cases, and quality attribute workshops to elicit and analyze NFRs. Once you have a list of NFRs, you need to prioritize them according to their value, urgency, and dependency. You can use methods such as MoSCoW, Kano, or pairwise comparison to rank and classify NFRs.

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Kemi Lewis

Getting Magic Done Practitioner | C-Suite Advisor | Systems Engineering Yoda| Chief Systems Engineer | IFEC Expert | Gracie Jiu-Jitsu Brown Belt
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Prioritize non-functional requirements from the start. Integrate security, performance, and usability into every development phase. Define them with concrete metrics. Implement continuous testing to catch issues early. Don't treat them as afterthoughts. Allocate resources specifically for these areas. Ensure the team understands their critical importance. Make them integral to the project's success. Stay focused and get it done.

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2 Specify and document NFRs

The next step is to specify and document the NFRs in a clear, consistent, and measurable way. You can use different formats and notations, such as natural language, tables, diagrams, or models, to express the NFRs. However, you should avoid ambiguity, vagueness, and inconsistency in your specifications. You should also use metrics, indicators, or criteria to define the expected level, range, or threshold of the NFRs. For example, you can specify the security NFR as "the system shall encrypt all data in transit and at rest using AES-256 algorithm" or the performance NFR as "the system shall respond to user requests within 2 seconds 95% of the time".

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3 Validate and verify NFRs

The third step is to validate and verify the NFRs with the stakeholders and the system. Validation is the process of checking whether the NFRs are correct, complete, and consistent with the stakeholder needs and expectations. Verification is the process of checking whether the system meets the NFRs as specified and documented. You can use various techniques and tools, such as reviews, inspections, walkthroughs, prototyping, testing, simulation, or monitoring, to validate and verify the NFRs. You should also involve the stakeholders in the validation and verification activities and collect their feedback and approval.

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4 Manage and trace NFRs

The final step is to manage and trace the NFRs throughout the system lifecycle. Management is the process of controlling and coordinating the changes, dependencies, and conflicts that may arise among the NFRs and other requirements. Traceability is the process of establishing and maintaining the links and relationships between the NFRs and other artifacts, such as design, code, test, or documentation. You can use tools such as requirements management software, traceability matrices, or traceability graphs, to manage and trace the NFRs. You should also monitor and report the status and progress of the NFRs and communicate them to the stakeholders.

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5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How do you deal with non-functional system requirements such as security, performance, and usability?

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1 Identify and prioritize NFRs

2 Specify and document NFRs

3 Validate and verify NFRs

4 Manage and trace NFRs

5 Here’s what else to consider

System Requirements

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