What are Functional Requirements: Examples, Definition, Complete Guide
What are functional requirements? This is a question that often confuses business owners and developers alike. A functional requirement can be thought of as a product feature that the user detects. It might be an obvious feature, like a large Add to Cart button. But it can also be a less obvious feature, like correctly calculating the sales tax for the user’s online purchase. In this complete guide, we will break down functional requirements into their simplest forms and give you examples of each type. We will also define what each type of requirement means for your business and how to go about creating them.
What are Functional Requirements?
A functional requirement is a statement of how a system must behave. It defines what the system should do in order to meet the user’s needs or expectations. Functional requirements can be thought of as features that the user detects. They are different from non-functional requirements, which define how the system should work internally (e.g., performance, security, etc.).
Functional requirements are made up of two parts: function and behavior. The function is what the system does (e.g., “calculate sales tax”). The behavior is how the system does it (e.g., “The system shall calculate the sales tax by multiplying the purchase price by the tax rate.”).
Types of Functional Requirements
Here are the most common functional requirement types:
- Business Regulations
- Certification Requirements
- Reporting Requirements
- Administrative Functions
- Authorization Levels
- Audit Tracking
- External Interfaces
- Data Management
- Legal and Regulatory Requirements
Creating Functional Requirements:
When creating functional requirements, it is important to keep in mind that they should be specific, measurable, achievable, relevant, and time-bound (SMART). In other words, your functional requirements should:
- Be specific about what the system should do
- Be measurable so that you can tell if the system is doing it
- Be achievable within the timeframe you have set
- Be relevant to your business goals
- Be time-bound so that you can track progress
By following these guidelines, you can be sure that your functional requirements are clear and will help your development team build the right product.
To give you a better understanding of functional requirements, let’s take a look at some examples.
Example # 1
: A user shall be able to log into the system using their username and password.
In this example, the function is “login” and the behavior is “The system shall allow a user to login using their username and password.”
Example # 2
: The system shall calculate the sales tax for the user’s purchase.
In this example, the function is “calculate sales tax” and the behavior is “The system shall calculate the sales tax by multiplying the purchase price by the tax rate.”
Example # 3
: The system shall send a confirmation email to the user after they have successfully placed an order.
In this example, the function is “send confirmation email” and the behavior is “The system shall send a confirmation email to the user after they have successfully placed an order.”
As you can see, functional requirements are specific statements about what the system should do. They are different from non-functional requirements, which define how the system works internally (e.g., performance, security, etc.).
When creating functional requirements, it is important to keep in mind that they should be specific, measurable, achievable, relevant, and time-bound (SMART). By following these guidelines, you can be sure that your functional requirements are clear and will help your development team build the right product.
How are functional requirements different from non-functional requirements?
Functional Requirements, as the name suggests, describe the functions of the system to be designed. It is a description of what the system will be and how it will function to satisfy user needs. They provide a clear description of how the system is supposed to respond to a particular command, the features, and what the users expect.
Non-functional requirements explain the limitations and constraints of the system to be designed. These requirements do not have any impact on the functionality of the application. Furthermore, there is a common practice of sub-classifying the non-functional requirements into various categories like:
- User Interface
Sub-classifying the non-functional requirements is a good practice. It helps when creating a checklist of the requirements that are to be met in the system to be designed.
Non-functional requirements are as important as functional requirements are. If functional requirements specify what a system should do, non-functional requirements describe how it will do it. For example, the new application shall provide us with the final list of all connected users. That is a part of functional requirements. If the requirement says that the system would only work on a Windows and a Linux system, that would be a part of non-functional requirements.
The only difference between the two is that the system can not function without satisfying all the functional requirements. On the other hand, the system will give you the desired outcome even when it does not satisfy the non-functional requirements.
Functional requirements are the key to success for any software development project. By creating functional requirements, you ensure that everyone on your team understands what needs to be built and can prioritize their work accordingly. In our next post, we’ll discuss how to create functional requirements using the Visure Requirements ALM Platform. If you want to learn more about functional requirements or get started with creating them yourself, request a free 30-day trial at Visure Requirements ALM Platform today.