Functional vs Non-functional Requirements: List & Examples

Deciphering a project’s requirements before its inception is an excellent way to regulate a project development process. A well-documented list of requirements is essential when working on any project since it enables managing entities to align time and resources for a well-curated plan. There are cases when the absence of these requirements may even lead to the project’s failure. 

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You can avoid these issues simply by defining functional and non-functional requirements. Some non-functional needs are challenging to define, even when functional requirements may be self-evident.

Requirements must be precisely defined for a project to succeed. These requirements also ensure that the client and development team work towards the same objectives. You must articulate requirements to avoid misunderstandings between the team and the client to raise the likelihood of a project succeeding. 

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Let’s have a look at the kind of impact defining functional and non-functional requirements brings into the system:

Definition of terms and roles

When you have a set of requirements, all the stakeholders, like the developers, program managers, and the other team members, are aligned on the same page. This helps in avoiding any misunderstanding while a project is underway. 

Reduction in communication time

Working closely with the BA guarantees shorter development times and significantly defined requirements. A similar strategy lowers the project’s cost and the time needed for communication during the development phase.

Brings in precision

With a list of detailed requirements, one can estimate the project’s development time with utmost precision. Also, the pre-decided requirements help you ascertain the cost of the project.

Prediction of possible mistakes

When you have a list of requirements, it becomes easy to visualise the project during its inception stage. Hence, it becomes easy to identify any error that might affect the project at a later stage. Therefore, having a set of requirements helps predict mistakes and saves time and money. 

Curating predictable projects

The quality of the requirements and the ready-to-go wireframes help the developers predict the project results. Hence, you can analyse if a project will meet your expectations by having the functional and non-functional requirements at your disposal. 

What are Functional Requirements?

Functional requirements are those requirements that specify what a system should do in a specific condition. A functional requirement will explain the system’s specific behaviour or function when given circumstances are met. 

These requirements comprise the product features and capabilities that web and app developers must incorporate into the solution and how the system should behave under particular circumstances. Such specifications must be exact for both the development team and stakeholders.

There are several things that a functional requirement includes:

• Administrative functions
• Audit Tracking
• Authentication
• Authorisation levels
• Business rules
• Certification requirements
• External interfaces
• Historical data
• Reporting requirements
• Transactions modifications

In business analytics, you must include these elements to ensure the output generated is up to the mark. You must create a functional requirements specification document to capture all functional requirements. They could be user stories and use cases to offer deeper comprehension. 

Contents of the Specification Document

Different sections are a part of the specification document. Some of these important sections include the following:

Purpose: The purpose section covers the background of a project along with the system overview to ensure that the project’s objectives are summed up briefly. 

Overall description: You must also mention your vision for the project and the business rules governing it. You must also include the assumptions that you are making during the project. 

Specific requirements: Specific requirements may range from database to functional requirements specific to the project. 

Use Cases: Use cases outline how the system interacts with outside users to accomplish specific objectives. The use cases have three main elements: actors, system functional requirements, and goals. 

User Stories: User stories are explanations of software features written from the end user’s viewpoint. The document provides examples of user interactions with the solution.

What are Non-Functional Requirements?

While the word ‘requirement’ might be used generically, there is a difference between functional and non-functional requirements. A non-functional requirement specifies how a particular system performs a specific function. It defines the system’s behaviour and how the project objective should be delivered. 

In business analytics, the non-functional requirements cover all the demands not captured under the functional requirements. They define standards that evaluate system performance as opposed to particular behaviours.

While a functional requirement is important, meeting all the non-functional requirements is not mandatory. However, non-functional requirements are vital as they directly impact the usability of a solution. 

Some of the typical non-functional requirements include the following:

• Availability
• Capability
• Data Integrity
• Environmental 
• Performance
• Recoverability
• Regulatory
• Reliability
• Scalability
• Security
• Serviceability
• Usability

Several parties in a system ensure that the non-functional requirements are duly met. The non-functional requirements affect the system’s users, and hence, they are important. 

How to Define Non-Functional Requirements?

Let us now try to understand how analysts define the non-functional requirements:

• Defined classification: It is essential to classify and define the requirements carefully. You can segregate the non-functional requirements into three groups, namely operation, revision, and transition. The classification makes these requirements noticeable and is then picked by the relevant stakeholders during the project. 
• Have a list of pre-defined questions: You must have a list of questions ready to ensure that the productivity of the development teams increases. These questions will also help you prepare for workshops and other reactive interviews. 
• Invented wheels: You must use the ‘invented wheels’ and repurpose the requirements created for other systems. This is because software systems have much in common regarding non-functional requirements. 
• Automated Testing Tools: Use tools for automated testing like Selenium, TestComplete, and Appium. These tools will make it easier to monitor the performance of your product and expose more non-functional requirements.

Exploring Functional vs Non-Functional Requirements

Now that you know what functional and non-functional requirements are, it is important to understand how they differ. Let’s have a look at the functional vs non-functional requirements below:

While both of these requirements are different from each other, both of them are significant when designing software. 

Gathering Functional and Non-Functional Requirements

Collecting and documenting all of your functional and non-functional requirements is essential to a well-curated development process. The best way to define these requirements is to bring all the stakeholders together. These requirements can easily be divided into four groups:

• Administrative functions
• Business requirements
• System requirements
• User requirements

Once you have defined all the functional requirements, it is time to move to the non-functional requirements. You need to take care of the following aspects:

• Performance
• Reliability
• Scalability
• Security
• Supportability
• Usability

Both of these requirements will decide the direction of your project. Therefore, you must define them with utmost care and precision. 

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Conclusion

With the onset of business analytics making its way as an indomitable part of any organisation, knowing its key aspects, like functional and non-functional requirements, is equally valuable to assist project development. From creating a regulated project structure to utilising optimum resources towards enhanced revenue generation, these requirements can pave the way for improved software production. 

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