====== The Significance of Non-Functional Requirements in Product Development ======

By Uchunzhyan Mikhail (msuchunzhyan@edu.hse.ru)

===== Introduction =====

Studying the sometimes overlooked but important component like non-functional requirements is very interesting when getting familiar with the complexities of software and product development. Non-functional requirements are very important to the success of a product because they ensure that it meets not only user expectations, but also industry standards and functional needs. The concept of non-functional requirements, their importance and how they affect the development process will be discussed in this essay.

===== What are non-functional requirements? =====

Non-functional requirements, which are sometimes called quality attributes or non-behavioral requirements, are critical elements that determine how well a product performs, is usable, safe, and meets other quality standards. Non-functional requirements define "how" the system should function, as opposed to functional requirements, which list specific features and capabilities. Non-functional requirements cover a large number of system characteristics, such as: performance, scalability, reliability, security, usability, and compliance with industry regulations. 

{{ :arch:main_types_of_non-functional_requirements_2.png?direct&600 |}}

//Picture 1. Main types of non-functional requirements.//

===== Difference between functional and non-functional requirements =====

The importance of non-functional requirements to the overall quality of a product is one of its most significant characteristics. Non-functional requirements define "how" the product should work, while functional requirements define "what" the product should do. As an example, let's take a web program that must serve hundreds of thousands of concurrent visitors. The exact capabilities that the application must provide, such as user registration, login, and content sharing, would be specified in the functional requirements. Non-functional requirements in this case include the responsiveness of the application, the ability to manage traffic, and security measures to keep user data safe. A functionally complete application that misses these non-functional aspects may be unresponsive, insecure, or simply unusable for its intended purpose.

In the product development process, satisfying non-functional criteria is sometimes more difficult than functional criteria. This is because non-functional requirements are often arbitrary and subject to different interpretations. For example, "usability" is a non-functional need that differs from user to user. What is understandable to one person may be difficult to understand to another. Because of this, it is very important to quantify and measure non-functional needs. For example, application response time should be described as "less than 2 seconds for 95% of user interactions." This quantification helps set clear expectations and allows developers to design, test, and optimize the product accordingly.

{{ :arch:the_difference_between_functional_and_non-functional_requirements_2.png?direct&450 |}}

//Picture 2. The difference between functional and non-functional requirements using a website example.// 

In addition, functional and non-functional requirements depend on each other. The fulfillment of functional needs can have a direct impact on non-functional aspects. For example, a functional requirement to process a huge amount of data may affect performance of the system which relates to non-functional requirements. This interaction emphasizes the need for a complete approach to requirements development, where both functional and non-functional needs are considered simultaneously.

===== The importance of non-functional requirements =====

In product development, the lack of clearly defined non-functional criteria can cause a number of problems. These include scope creep, when stakeholders are constantly adding new non-functional requirements, resulting in project delays and increased costs. In addition, without clearly defined non-functional criteria, developers may prioritize functionality over critical quality attributes, which can lead to an unreliable or unsafe product. Thus, defining and managing non-functional requirements is necessary to stay within the scope, schedule, and budget of the project.

Taking non-functional needs into account in product development goes beyond technical considerations. They have a direct impact on the end-user experience, which in turn affects how well a product performs in the marketplace. For example, a mobile app that takes a long time to launch can deter users and increase bounce rates. Similarly, an online service with weak security procedures may have a data breach that damages its brand. Thus, non-functional requirements have a great impact on customer satisfaction, loyalty and trust.

In addition, compliance with regulatory requirements depends on compliance with non-functional requirements. A number of industries, including healthcare, banking and aviation, have strict regulations and standards that products must meet. These standards often contain performance, reliability and non-functional data security requirements. Ignoring these standards exposes organizations to serious legal and financial consequences.

===== Conclusion =====

In conclusion, it is very important for someone expecting to work in product development to understand the critical importance of non-functional requirements. In addition to determining the quality, performance, and safety of a product, they also affect customer satisfaction, regulatory compliance, and overall project success. Effective management of non-functional requirements requires the use of both accurate, quantifiable specifications and an overarching requirements strategy. If neglected, a product can fail due to delays, budget overruns, and other factors. Thus, to ensure the release of products that excel not only in capability but also in quality, non-functional requirements must remain at the center of attention in an ever-changing software and product development environment.

===== Personal opinion =====

As for my personal opinion, I consider the topic of non-functional requirements as one of the most important elements of the development process. It's easy to get carried away with creating new features and functions, but the user experience and reliability of a product is actually determined by often-overlooked non-functional requirements. I believe that a product must do more than just "work." To meet user and stakeholder requirements, it must function effectively and reliably. Successful and sustainable product development depends on understanding the delicate balance between functional and non-functional requirements. This harmony, in my opinion, is the essence of high quality software and product development.

===== References =====

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