You are thinking about buying a coffee machine. You want it to make espresso, americano, and cappuccino as well as froth milk whenever you need it. You also would like it to be red, work quietly, and make a cup of coffee within 10 seconds. Consider this as a simple explanation of functional and non-functional requirements.

Requirement analysis is crucial for project success. It helps Business Analysts and Project Managers define the needs and conditions to be met, set the right goals, and create necessary product documentation.

The Role of Software Requirements

Any project starts with an idea and a range of criteria to be met. The requirements outline the features a product should have in order to address the needs of both parties — business and end-user.

First, all the requirements can be divided into three main categories that describe the business, user, and system guidelines.

Software Requirements Types

Business requirements describe the high-level goals of the company and stakeholders’ vision of what the software should do in terms of their business.

User requirements define what users can do with the system, their needs, and a list of activities they expect to perform.

System requirements are the building blocks that are used to create a software solution in practice. They can be functional and non-functional.

Clearly defined requirements help the development team and client move in the same direction and achieve initial goals. Generally, they are captured in requirement documentation that enables covering the following moments:

It is important to pay attention to detailed requirements beforehand as further adjustments during the development process often cause project delays and cost increase. On top of that, there is even a risk of project failure if the key points are determined imprecisely.

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Understanding the differences between functional and non-functional requirements helps deeply analyze project needs and identify the right scope of work.That being so, it results in cost optimization as your software product will include only the most significant features and functions. Furthermore, knowing the differences will empower you to support customers with a better experience.

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What Are Functional Requirements?

What Are Functional Software Requirements

To put it in simple words, functional requirements (FRs) describe the basic software system behavior. It points out what the application should do and what should not in order to work in a trouble-free manner.

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When we talk about the features and functions the product must have to meet user requirements, we imply functional requirements. They include the actions users take to interact with the system as well as specific operations the system should perform. Usually, these operations are data input and output, calculations, or business flows.

Functional requirements are covered in a software requirement specification (SRS) that provides detailed descriptions of the product functions and capabilities. This document enables considering key moments of the project, addressing the needs, and ensuring a smooth and efficient development process.

Commonly, SRS documentation contains such important parts as:

Everything may sound easier in theory than in practice. If it is still puzzling to determine the FRs for your project, then let’s move to the list of realistic examples. They will allow you to have a better idea of what kind of features and functionalities you should identify in the first place.

Examples of Functional Software Requirements

Whether it comes to a web application project or mobile app development, there is a variety of functional requirements that apply to both cases. The examples include:

If we delve even deeper, then more detailed examples of functional requirements would be the following:

What Are Non-Functional Requirements?

What Are Non-Functional Software Requirements

Contrary to functional requirements, non-functional requirements (NFRs) define the quality attributes of the software system. They outline how the system should perform and the ways the product should behave.

Even if, for some reason, these requirements are neglected, the system will still provide its basic functionality. Then you might ask why they are important at all? A short answer is non-functional requirements immensely impact the user experience. And user experience is something you would not want to ignore.

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Non-functional requirements are essential to ensure the overall usability and efficiency of the software solution. They highlight particular conditions for the system to operate under, rather than certain behavior.

While underestimating NFRs leads to the poor user experience and inability to meet their expectations, overestimating causes the rise in project costs. Thus, it is vital to define the most significant requirements to deliver a successful product and stay on budget. Brainstorm ideas with all stakeholders, classify NFRs according to execution and evolution qualities, and engage with your development team.

Examples of Non-Functional Software Requirements

Similarly to functional requirements, we suggest looking through some examples of NFRs to streamline the process of their identification. Here they are:

Below you can find more specific practical examples of non-functional requirements:

Functional vs Non-Functional Requirements

Functional vs Non-Functional Requirements

All the information covered above serves as a guideline to pave the way for a top-notch software solution. We have summarized the key differences between functional and non-functional requirements so you could have a brief look at them once again.

Functional Requirements
Non-Functional Requirements
Key Question
What should the system do?How should the system perform the tasks?
Product featuresProduct properties
User requirementsUser expectation and experiences
Use casesQuality attributes
System functionalitySystem performance
Significance level
Identification difficulty
Quite evident to defineQuite hard to discover, unobvious

So Does It Make a Difference?

To make a long story short, functional requirements describe what features and functions a software system must have to enable flawless and uninterrupted operation. They are derived from the business idea and responsible for the basic system behavior.

On the other hand, non-functional requirements help define how the system should work and how to provide users with a seamless experience. While identifying NFRs, you should consider the performance, convenience, and usability of your future product.

Although functional and non-functional requirements sound easy to reveal, they often leave companies perplexed. Understanding the differences between them is essential for a successful project. Thus, having a software development partner by your side will help cast light on the subject, optimize project time and costs, avoid major pitfalls, and ultimately deliver a robust product.

Velvetech is staffed with experienced teams of BAs, PMs, and developers who aspire to know more about your project idea. Our expertise goes far beyond project estimations and ensures custom software solutions meet the most challenging requirements. Share with us your vision and we will help with its realization.

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