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Mobile App Development : Functional and Non-Functional Requirements

Have you ever noticed that unclear requirements account for 41% of a company’s IT development budget? In fact, these ambiguous requirements cause a 60% increase in the development budget and timeframe estimations! This could imply that the damage has already been done before you start the endeavour.

That is why today’s article is so important. As projects progress and deadlines approach, the client will certainly cut some features that appear to be non-essential. This is done in order to save time and money. Non-functional needs are the most common non-essential requirements.

Now, if you could find a means to categorise essential and non-essential requirements from the outset, you might spend a significant portion of your resources to the essentials while maintaining any progress achieved on the non-essentials.

That is why it is critical for all stakeholders involved in app development to understand both functional and non-functional needs. This keeps projects short, saves money, reduces waste, leads to a more holistic, well-rounded development, and speeds up the time to market.

So, what are the differences between functional and non-functional requirements?

Functional RequirementsFor Mobile App Development

Simply expressed, functional requirements specify what an app is expected to accomplish. They are the essential functions without which the app will not work or accomplish its goals.

These are prerequisites that must be met and that can’t be skipped. Before the development can begin, these needs must be clearly articulated and documented as part of the development contract. Before the operation is processed and the output is sent to the user, they must be recorded as inputs that must be given to the system.

The following are some instances of functional requirements:

  • Authentication
  • Transactions and checkouts
  • Authorizations
  • Data from the past

Non-Functional Requirements For Mobile App Development

Non-functional requirements are those that specify how the programme should do a specific task. In essence, these are the app’s quality attributes that determine the app’s user experience. They’re also known as non-behavioral criteria, and they’re prioritised by how important they are to the app’s operation. This gives them some flexibility, allowing them to bypass a few in the event of time, budget, or technological constraints.

The following are some examples of non-functional requirements:

Loading speed Time taken to deliver server response
Time it takes for the user to respond
Limits on data usage

It’s time to put everything into perspective. A functional need for a meal ordering mobile app, for example, would be:

Restaurants in the vicinity are shown.
Menus are being displayed.
Placement of orders
Transaction processing, for example.

The following are non-functional requirements for a meal delivery mobile app:

Every 5 minutes, refresh the restaurant listings.
Within 10 seconds after pressing the menu button, the menu will be loaded.
Within 2 seconds following payment, an order confirmation must be sent.
As you can see, functional requirements are critical aspects of an app that must be considered during development. Is this to say, however, that non-functional requirements aren’t important?

In reality, non-functional criteria are critical to the app’s performance and user experience. If an app’s functional requirement is to pull up a list of sushi restaurants in the area, but it takes more than 30 seconds, the user is likely to exit the app, even if the functional demand was eventually met.

Having a proper balance of functional and non-functional criteria is vital to ensure that an app development project is successful, under budget, and on time. If the need arises for any app attributes to be removed, you’ll be able to quickly determine which ones to remain and which can be overlooked for the time being.

What’s the use of distinguishing between functional and non-functional requirements?

On the surface, the line of demarcation is clear. It appears to be a no-brainer to distinguish between functional and non-functional criteria. Why is it so critical to collect, classify, and document these properly?

To keep the development cycle running smoothly and avoid lengthy reviews later on, it’s critical to classify functions thoroughly and understand what you’re dealing with.

According to a survey, 68 percent of projects that use good communication and proper documentation are more likely to accomplish project goals.

Another study indicated that unclear requirements were responsible for 32 percent of IT project failures, making them one of the leading causes of IT project failure. Capital is wasted, deadlines are missed, and overall product quality suffers as a result of unclear requirements.

To avoid all of this, it’s critical to specify the scope and needs of the project. This necessitates a clear distinction between functional and non-functional needs, as well as a clear understanding of development priorities.

Understanding the difference between functional and non-functional needs is beneficial to us –

Catch errors early on – reviews tend to get more expensive as time passes. Early detection of errors saves time, money, and morale, leading in improved app development.

Helps structure priorities – Knowing your functional and non-functional requirements allows you to keep a few non-functional criteria flexible, which helps structure priorities. If money or time constraints force you to eliminate some features, you’ll know exactly what you need to preserve and what you can go without.

Prototypes’ Role in Defining Requirements

Now that you know how critical it is to understand your requirements and distinguish between functional and non-functional requirements, it’s time to figure out how to make sense of it all.

Building a mobile app prototype is one of the finest methods to keep a clear project goal and everyone on the same page. Without creating a single line of code, this allows you to get as close to envisioning an actual programme as possible. Knowing what else you have room for depends on your ability to visualise all of your functional requirements as well as the significant non-functional requirements. You’ll be able to plan a clear path of action and observe how your solutions will work this way.

What Are Non-Functional Requirements For Mobile App Development and How Do You Define Them?

The tough phase is about to begin. Non-functional needs, in contrast to functional requirements, are more difficult to define. There are several that we presume everyone is aware of, such as sending confirmation emails in less than 5 seconds.

As a result, it’s critical to spell out all non-functional requirements at the outset of your project. 

Create a list – first and foremost, get down with your stakeholders and team and have a brainstorming session with all of your ideas on the table. Before you begin to classify and organise them, make a list of all of them.

Use pre-defined classes — You might simply categorise non-functional requirements using pre-defined classifications such as operation, business, and administrative.

Use automated testing – Automated testing technologies like as Selenium, Appium, TestComplete, and others can help you quickly examine the performance of your project, identifying any non-functional needs you may have overlooked.


When it comes to developing commercial apps, every resource counts. Understanding your functional and non-functional needs throughout app development can help you save time, money, and human resources. This way, you’ll know precisely how long you’ll have to keep that can of Coke down.

Once you have your requirements, you can immediately begin working on the functional needs, leaving room for changes based on iterations and customer input. You’ll know all the critical components you want to preserve when it’s time to scrape deadlines and add a few bells and whistles.

As a result, start by clearly mapping out your functional and non-functional needs, and you’ll be able to breeze through the development process.

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