The Role of Non-Functional Requirements in Project Success

Every software project will take a pre estimated amount of time to complete. However, many times projects take longer and go over budget. One of the reasons for this is that non-functional requirements aren’t considered from the beginning.

Usually, software development projects focus mainly on functional requirements. Sprint after sprint, the product owner chooses which user stories will add value and are most relevant to the final product.

However, some requirements are not directly correlated to the final product functionality but are critical for ensuring that it meets user expectations and business needs. These are known as non-functional requirements (NFRs).

In this article, we’ll explain what NFRs are, their role, and how they relate to functional requirements.

What Are Non-Functional Requirements? (NFRs)

Non-functional requirements (NFRs) define how a system operates rather than what it does. Unlike functional requirements, which specify particular behaviors or functions of a system, non-functional requirements focus on aspects like performance, security, usability, and scalability.

Although they may seem trivial initially, NFRs are vital to the system's success. For example, a correctly defined/developed/tested software product may fail when it goes into production if performance, scalability, security, usability, or maintainability aren’t considered.

Satisfying the NFRs ensures the system complies with business, customer, and market requirements, industry standards, and regulations. Lack of compliance often causes increased cost, rework, privacy, security, and legal exposure issues.

Correctly identifying NFRs in every agile project is a critical task. If overestimated, they can increase the solution's cost and complexity; if underestimated, they can result in an inadequate product.

Functional vs Non-Functional Requirements

Types of NFRs (Non-Functional Requirements Examples)

NFRs describe various quality attributes with which a system must execute. Often, they are specifications related to the solution's architecture and infrastructure. Some of the most common include performance, scalability, security, usability, maintainability, fault tolerance, interoperability, robustness, and compatibility.

Certain design or development restrictions, usually incorporated by system and solution architects, can also be found. For example, the use (or avoidance) of a particular programming language or the required interoperation of the solution with other platforms or systems.

It is important to consider the best practices when detailing NFRs:

• They must be clear and understandable. Avoid ambiguities and technological jargon. Use graphics to highlight these requirements.

• They must be specific, precise, and complete. They must also be consistent, cover all scenarios, and avoid contradictions, vagueness, or generalizations.

• They must be testable. Include specific expected results.

• They must be feasible and affordable. Keep the focus on the scope of the solution and user expectations.

Here are some NFR samples:

Testing NFRs

The “Agile Testing Matrix” (Brian Marick, Agile Testing) is an excellent guide for testing NFRs.

NFR tests correspond to quadrant 4. This type of test requires several tools (automation, monitoring, loading, etc.) that allow the proper test generation and measurement. These tools also provide a means to report the system execution results to confirm compliance with the NFRs and design restrictions.

Wrapping Up

Non-functional requirements complement the scope of every software project. When agile teams know and understand them, they can make better development decisions and ensure the delivery of a solution that meets the stakeholders' requirements and satisfies their expectations, executes with quality, and respects the restrictions and limitations.

At Oshyn, our software development teams pay close attention to the functional and non-functional requirements required for a successful project. It’s why leading enterprises trust us to deliver the digital experiences that connect them with their customers.

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