Imagine you’re designing your dream house. You’ll start with planning the number of rooms. You’ll add a modern kitchen and a cozy balcony, too. But what if you forget the other important details? This includes the ventilation, lighting, and insulation. You’ll get a house that looks amazing. Yet, it’ll be terrible to live in. This is exactly what happens to software if you only focus on the functional requirements. Suppose you don’t focus on the non functional requirements. You will have an app that looks great but doesn’t work correctly. Functional vs non functional requirements work together.
Did you know that 39% of software projects fail? Why? Because of poorly defined requirements! This is why we’ve created this blog. It will explain the differences between functional vs non functional requirements. By the end, you’ll know why they’re so important.
What are functional requirements?
On the days we struggle, we tend to imagine, “What if there was a device that could do this?” Since it’s just imagination, it doesn’t have limits. But in reality, what you want a device to do is more realistic. When you define what a system should do, those requirements are functional. Here’s an example:
Chair 🪑 → “Must support the weight of an average adult without collapsing.”
Characteristics of functional requirements:
Functional requirements are basic and easy to understand.
- These requirements make everything clear. What should the product do? What are its functions? They focus on the product’s behavior.
- They focus on what the user wants. These requirements are like standards that you set for your product before delivering it to your customers.
- A Proof of Concept (POC) takes place to test the feasibility of a product before setting functional requirements. This proof of concept (POC) ensures that the product is practical and achievable.
What are non-functional requirements?
You’ve got a product idea, and you know what it’ll do. What about the “how”? This is where nonfunctional requirements come in. They revolve around how a product will complete its requirements. 50-80% of product defects end when you follow non-functional requirements correctly,
Must last at least 5 years under normal usage
Made from sustainable or recyclable materials where possible
Made from high-quality wood to support up to 120 kg safely
Characteristics of non-functional requirements:
In functional vs non functional requirements, nonfunctional requirements handle how a product would operate:
- They focus on the usability of a product. This means how easy or difficult it is for the user to use the product.
- Nonfunctional requirements manage the performance and security of a product. In software, this means managing data privacy. It also help deliver high performance.
- These requirements manage how much stress a software can handle. How will it grow and scale?
What are the differences between Functional vs Non Functional Requirements?
37% of project failures are a result of poor requirements. This is why it’s essential to set functional requirements. Let’s go deeper to understand the core differences. In functional vs non functional requirements:
Focus
Functional requirements focus on what a system should do. It’s more task-specific. This is why functional requirements tend to change. They focus on the user’s needs and feedback.
In nonfunctional requirements, the focus is on how a system performs. It’s more product-specific. Functional requirements focus on user expectations. This is why nonfunctional requirements stay stable. They do not change once you set them.
Nature
Functional requirements are dynamic. New features are added and modified based on user feedback. They also change with the project’s scope. Sometimes, this causes features to be removed, too.
In contrast, nonfunctional ones remain stable. Once you define them, they are set. This is because they revolve around how a system should perform. They can still change if functional ones cause big changes. It’s because they handle the quality and usability of a software prototype.
Impact
The functional requirements focus on what a product does. This means they directly impact the core usability of a system. If you don’t apply them correctly, the system may not function at all. Think of an e-commerce site that doesn’t have a checkout page. It would be useless.
A product’s nonfunctional requirements impact its performance. This affects the user experience. If a product follows all the functional requirements, it will have all the necessary features. But if it doesn’t follow the nonfunctional ones, it will not satisfy the users. The product wilol end up slow and not secure.
Testing methods
Unit, integration, and user acceptance testing. These are functional tests. They verify if the system performs the expected tasks correctly. When they match the functional requirements, we move on to nonfunctional ones.
Non-functional requirements are tested through performance testing. This also includes security, stress, and usability testing. They ensure that the system works efficiently under different conditions. It also guarantees the software meets quality standards.
Dependency
The Functional requirements for a product are independent. They don’t depend on nonfunctional requirements. A system may not fulfill user needs. But, it can still exist with only functional requirements.
However, non-functional requirements depend on functional requirements. Without them, they have no meaning. Functional requirements always come first. Nonfunctional ones are set for them.
These are the key differences between functional vs nonfunctional requirements. Both are equally important in software development. Balancing them is important to deliver a user-friendly product. Everybody loves a good user experience.
What are the types of functional requirements?
Here are a few types of functional requirements:
Authentication
Functional requirements ensure that only authorized users can access the system. This includes user login, two-factor authentication, etc. These features are the basic requirements for software security.
User interface and user experience (UI/UX)
This defines how users interact with the system. It focuses on building a navigable and intuitive User Interface. This helps deliver a good user experience.
System integration
They describe how the system integrates with other systems. This includes APIs or third-party services. Setting clear requirements for integration helps avoid issues or rework later.
What are the types of nonfunctional requirements?
Here are a few types of nonfunctional requirements:
Usability
Nonfunctional requirements have a special focus on usability. They help make a product easy for a user to use. How long does it take to accomplish a task? or What are the load times? It manages the usability of a product from different points of view.
Privacy and Security
Users are always concerned about their safety. More than 84% of people have concerns about their security. Nonfunctional requirements focus on the privacy and security of software.
Performance
Performance is how a user interacts with the product and how the product reacts. Everybody wants high-performing software. Slow software can cut a company’s revenue by 30% per year! Nonfunctional requirements focus especially on performance.
What are the Examples of Functional vs Non Functional Requirements?
Without functional vs non functional requirements, software would not have any features. Noting them down will allow successful and error-free development. It will enable you to create a software prototype that delivers a great user experience. Let’s go through a case scenario to see how you would set the functional vs non functional requirements for your software.
Functional Requirements
Setting the functional requirements of your software means setting what it will do.
Case scenario
Now, let’s suppose you want to develop an e-commerce store. Let’s set the functional requirements:
- Your Buyers should be able to log in. This will allow them to access their cart and purchase history.
- Sellers should be able to add and remove products. They should also be able to add a category, names, and product descriptions.
- Buyers must be able to pay through PayPal or other methods online. After payment, they should receive a successful order confirmation.
- Users should be able to track order status. Admins should be able to update the status.
- The users must be able to receive notifications regarding their order.
- Buyers should be able to search for a product by name or category. They should also be able to filter products.
- They must be able to choose shipping methods.
Non Functional Requirements
For the non functional requirements, the e-commerce store will have different requirements:
Case scenario
For your e-commerce store:
- The website should load in 3 seconds. This should be the case for 95% of users who visit the site.
- On sale days, the website should be able to handle high traffic. This should be necessary during peak times, like an hour before the sale ends.
- Buyer data should be encrypted. The seller should have multi-factor authentication (MFA) to log in. Payment should be secure.
- The website should be mobile-responsive. It should comply with the Web Content Accessibility Guidelines.
- The system should log all transactions and activities for fraud detection. There should be an error tracking system.
- In case of failure, there should be a disaster recovery plan to restore operations.
- The website should support secure automated software updates. This should not affect the users or their privacy.
Wrapping up
Developing software for your business is a dream for everyone. Understanding the functional vs non functional requirements are vital for a software’s success. These requirements make the process easier. Every user wants a good user experience and high-quality software. So, setting these requirements is important no matter what your software goals are.
At Linkitsoft, we know functional vs non functional requirements. Partner with us to develop your software. We make sure to follow each requirement for your software. Connect with us today. Unlock new possibilities for your business.
