Written by: Andrew Fruhling, Chief Operating Officer at Calavista
In the world of software development, we often focus on what a system should do. We meticulously define user stories, create detailed use cases, and map out intricate workflows. But in this rush to nail down functionality, we often overlook a critical aspect of system design: non-functional requirements (NFRs).
What are Non-Functional Requirements?
Non-functional requirements define how a system should behave and what qualities it should possess. While functional requirements specify what the system should do, NFRs describe the manner in which it should do it. They encompass critical aspects like performance, security, scalability, and usability, which are essential for ensuring a system’s effectiveness and user satisfaction.
Many non-functional requirements end in “-ility” (e.g., usability, reliability, scalability), leading to this informal collective term. Several years ago, I worked for a company that called them “Standing Requirements.” This was based on the idea that new functional requirements would be defined for each release, but standing requirements would be defined once and stand for each release. Essentially, we defined levels of scalability, reliability, etc., and then identified what level we expected the application to achieve with each release. This approach helped maintain consistency and quality across different versions of the software, ensuring that core system qualities were always met.
Regardless of the term used, NFRs are critical to the success of your application.
Why NFRs Matter
Imagine you’ve built an e-commerce platform that perfectly executes every step of the purchasing process. It sounds great, right? But what if it takes 30 seconds to load each page? Or if it can only handle 10 concurrent users? Suddenly, your functionally perfect system becomes practically unusable.
Non-functional requirements are crucial for several reasons:
1. User Satisfaction: NFRs directly impact the user experience. A system that’s slow, unreliable, or difficult to use will frustrate users, regardless of its features. Meeting NFRs ensures that users not only can use the system but enjoy using it.
2. Business Success: NFRs often align closely with business goals. For example, high performance and scalability can support business growth, while strong security protects the company’s reputation and assets.
3. Competitive Advantage: n markets where multiple products offer similar functionality, superior non-functional qualities (like faster performance or better usability) can be the differentiator that gives your product an edge.
4. Cost Efficiency: Addressing NFRs early can prevent costly rework later. For instance, building scalability from the start is often easier and cheaper than trying to scale a system that wasn’t designed for it.
5. Risk Mitigation: Many NFRs (like security and reliability) help manage and mitigate risks to the business and its customers.
6. Regulatory Compliance: Many NFRs (like security and reliability) help manage and mitigate risks to the business and its customers.
7. Long-term Viability: NFRs like maintainability and scalability ensure that the system can evolve with changing needs, extending its useful life.
8. Operational Efficiency: Well-defined NFRs around performance and reliability can reduce operational overhead and support costs.
Consider our e-commerce platform example. A system that’s fast, secure, and easy to use not only satisfies customers but also reduces cart abandonment, increases repeat business, and builds brand trust. It can handle sudden traffic spikes during sales events, protect sensitive customer data, and adapt to new features or markets as the business grows.
Moreover, in M&A scenarios, software with well-implemented NFRs frequently command higher valuations. During due diligence, acquirers often closely examine how well the system performs, scales, and integrates – all aspects governed by NFRs.
By prioritizing NFRs, we’re not just building systems that work; we’re building systems that work well, meet business objectives, satisfy users, and stand the test of time. In today’s competitive and fast-evolving digital landscape, these qualities are not just nice-to-haves – they’re essential for success.
Some Example NFRs By Category
The Challenge of NFRs
While these categories provide a framework for thinking about NFRs, the real challenge lies in defining specific, measurable requirements for each category that align with your project’s needs. It’s not enough to say “the system should be maintainable” – you need to define what that means in concrete, SMART terms. These are very similar to the SMART goals used in general management techniques – i.e.: Specific, Measurable, Assignable, Relevant (or Realistic), and Time-Related).
For example, instead of a vague statement like “The system should be fast,” a SMART NFR might be:
“The system should load the home page in less than 2 seconds (Specific, Measurable) for 95% of users (Achievable) under normal traffic conditions (Relevant) when measured monthly (Time-bound).”
This approach helps in several ways:
- It provides clear targets for development and testing.
- It allows for objective evaluation of whether the requirement has been met.
- It helps in prioritizing and allocating resources effectively.
These requirements often interact with and influence each other. For example, implementing stringent security measures might impact performance, or focusing too heavily on scalability might make the system more complex and less maintainable. This is where the ‘Achievable’ aspect of SMART goals becomes crucial – ensuring that your NFRs are realistic given your constraints and the potential trade-offs.
The key is to find the right balance that meets your specific business needs and user expectations. This often involves prioritization and trade-offs, guided by a deep understanding of your project’s goals and constraints. By applying SMART principles to your NFRs, you create a roadmap that is clear, actionable, and aligned with your overall project objectives.
Remember, the goal is not to create perfect NFRs, but to create NFRs that are good enough to guide development effectively and ensure the resulting system meets both functional and quality requirements.
Additional thoughts on NFRs in the Development Process
Non-functional requirements should be incorporated into your development process.
- Identify them early in the project lifecycle
- Make them specific and measurable
- Prioritize them alongside functional requirements
- Test them throughout development, not just at the end
- Review and adjust them as the project evolves
Conclusion
In our quest to build feature-rich, functionally robust systems, let’s not forget the critical role of non-functional requirements. They may not be as flashy as new features, but they’re often what separates a good system from a great one. By giving NFRs the attention they deserve, we can create software that not only does the job but does it exceptionally well.
Remember, in the end, users don’t just care about what your software does—they care about how well it does it. And that’s the domain of non-functional requirements. Ignoring NFRs can mean the difference between having an application that takes the world by storm, and one that never gets any traction in the market.
