App Development: Grasping Functional and Non-Functional Requirements
As projects grow and deadlines roll out, there are some seemingly unnecessary features that will inevitably be overlooked by customers. This is done to save time and money. These nonessential requirements usually happen to be nonfunctional requirements.
Now if you found a way to classify essential and nonessential requirements from the very start, you could devote the chunk of your resources to the essential requirements, and not lose any progress made on the non-essentials if they get dropped.
That is why understanding functional and nonfunctional requirements in app development is so important to all stakeholders involved. Doing so keeps projects succinct, reduces cost, minimizes wastage, results in a more holistic, well rounded development and gets the product to market faster.
So what are functional and nonfunctional requirements?
Functional requirements
Simply put, functional requirements are requirements that define what an application is supposed to do. These are the main functions without which the app will not work or do what it is supposed to do.
These are requirements that must be met and cannot be ignored. As a development contract, these requirements should be clearly stated and documented before development begins. They must be recorded as an input that must be passed to the system, before the operation is processed and the output is passed to the user.
Some examples of functional requirements:
- Authentication
- Business core
- Transactions, checkouts
- Authorizations
- Historical data
Non-functional Requirements
Non-functional requirements are requirements that define ‘how’ the app must perform a certain function. In essence, they are the quality attributes of an app that define the user experience of the app. They are also known as non-behavioral requirements and are to be implemented according to their priority to the app function. This makes them flexible to an extent, making it possible to skip a few in case of time, budget or technology constraints.
Some examples of non-functional requirements:
- Loading speed
- Time taken to deliver server response
- User response time
- Data consumption limits
Time to put this all in perspective. For example, the functional requirement for a food ordering app would include
- Displaying restaurants in the area
- Displaying menus
- Placing orders
- Processing transactions, etc.
Non-functional requirements of the food delivery app would include:
- Refresh restaurant listings every 5 minutes
- Load menu within 10 seconds of clicking on menu button
- Order confirmation must be sent within 2 seconds of payment
As you can see, functional requirements are an integral part of an application and must be present during development. However, does that mean that non-functional requirements aren’t the important factor after all?
Non-functional requirements are actually extremely important to application performance and user experience. If the functional requirement of the app is to display a list of nearby sushi restaurants, but the app takes more than 30 seconds to do so, the user is likely to abandon the app even though the functional requirements were finally met.
Therefore, to ensure the success of an application development project, within budget and on time, it is very important to have a good balance between functional and non-functional requirements. This way, if a push occurs and some properties of the app need to be removed, you can effectively decide which properties should be kept and which can be removed at this point.
Why differentiate between functional and non-functional requirements?
On the surface, the demarcation is quite clear. Distinguishing between functional and non-functional requirements can seem like a non-functional person. Why, then, is it so important to collect, categorize and document correctly?
In order for the development cycle to run smoothly and not to have a thorough review in the later stages, it is essential that you carefully categorize the functions and know what you are dealing with.
A study found that 68% of projects that followed effective communication and proper documentation were likely to successfully meet project standards.
To reinforce this point, another study found that 32% of IT projects fail due to unclear requirements, making them one of the biggest culprits in a business failure. Unclear requirements result in wasted capital, delayed lead times and reduced overall product quality.
To avoid all of this, it is important to define the scope and requirements of the project. And that requires clearly defining functional and non-functional requirements, so that development priorities are clear.
Understanding functional and non-functional requirements helps us -
Streamlining communication — Clearly defining requirements helps ensure that all teams and stakeholders are on the same page. This avoids any deviation or misunderstanding along the way.
Clearly define roles and objectives — with all the requirements clearly stated, it is easier to define the roles of the team and who does what.
More accurate estimate — knowing what features will be built into the application will help give a fairly accurate estimate, both in terms of cost and time.
Find bugs early — reviews tend to get more expensive over time. Early detection of errors saves time, money and mind, helping the application to grow better.
Help structure priorities — knowing your functional and non-functional requirements allows you to retain flexibility for some non-functional requirements. If there are budget or time constraints, if there are some features that need to be removed, you’ll know what you need to keep and what can be delivered.
Role of Prototypes in Defining Requirements
Now that you know how important it is to know your requirements and categorize functional and non-functional requirements, it’s time to understand what this information means.
One of the best ways to keep the project vision clear and everyone on the same page is to create a mobile app prototype. This allows you to see as much of an actual application as possible without writing a single line of code. Being able to visualize all of your functional requirements and key non-functional requirements lets you know exactly what you still have room for. This way, you can set a clear plan of action and see how your solutions will work.
How to Define Non-Functional Requirements
This is the difficult part. Unlike functional requirements which are empirically certain, non-functional requirements can be difficult to define. There are things we think everyone knows, like sending a confirmation email within 5 seconds. However, if they are not clearly defined, there is a notable situation where the confirmation email will be delayed when the network is down and result in a very bad user experience.
This is why it is important to clearly define all non-functional requirements at the start of your project. Some of the ways to do this would be –
Brainstorm a list — first and foremost, sit down with the stakeholders and your team, and have a jam session with all ideas on table. Note them all down before you begin to classify and sort.
Use predefined classifications — you could simply use predefined classifications like operation, business and administrative, categorizing the different nonfunctional requirements under these. This would help you prioritize and know what you need to tackle first.
Use automated testing — Selenium, Appium, TestComplete and other automated testing tools help assess your project performance quickly, revealing any nonfunctional requirements you may have missed.
Conclusion
When it comes to business application development, every resource matters. Understanding your functional and non-functional requirements can help you save time, money, and human resources in application development. Clearly defining functional and non-functional requirements is like having a detailed roadmap with clearly marked breakpoints. This way you know exactly how long you need to keep your soda can.
Once you know your requirements, you can start immediately with the functional requirements and leave room for changes based on iterations and customer feedback. When it’s time to set some deadlines and pop a few bells and whistles, you’ll know all the important ingredients you want to keep.
Therefore, clearly describe your functional and non-functional requirements up front and you will end up going through the development process without a hitch.
