It’s important for a product to work properly and have distinguishable features. With nonfunctional requirements, you can build a product with unique properties. Knowing examples of nonfunctional requirements and how they work in an application can help you design a system that meets the needs of your end users. In this article, we define nonfunctional requirements and explore the best practices for designing product properties.
What is a nonfunctional requirement?
A nonfunctional requirement is an attribute that dictates how a system operates. It makes applications or software run more efficiently and illustrates the system’s quality. Nonfunctional requirements differ from functional requirements in the following ways:
Mandatory vs. non-mandatory: In contrast to functional requirements, nonfunctional features are not mandatory for a system to operate. Instead, these features can help differentiate an application from other products on the market.
Basic operations vs. additional features: Functional requirements encompass what a system does, while nonfunctional requirements cover how a system completes a task. For example, the functional duty of a camera is to take pictures. The nonfunctional duty is to take pictures with enhanced focus and clarity.
Intended purpose vs. customer expectations: While functional requirements focus on the purpose of an application, nonfunctional requirements center on the users’ expectations, such as the product’s performance.
Top 9 examples of nonfunctional requirements
Here are nine examples of nonfunctional requirements and their significance to applications:
Speed determines how fast an application responds to commands. For example, if you type a word into a search engine, the speed of the engine determines how quickly you receive search results. Speed also involves assessing a system’s ability to manage an increasing workload as you use different applications at the same time. For example, a user might take pictures with a photo application while listening to music with an audio application. You can test the speed of a device by running multiple programs simultaneously and measuring how quickly they yield results.
To protect sensitive data, you may consider developing nonfunctional security features. For example, professionals at healthcare facilities use secure databases to store patients’ medical records. The security on their databases may include firewalls to prevent unauthorized access. Here are examples of typical security measures on software:
Account creation: Systems may require users to create accounts to access applications that store information and display profiles. A security system typically grants access to accounts when users enter the correct username and password.
Password generation: An application may not grant access until the user creates a strong password. For example, a strong password might contain a certain number of characters and a capital letter.
Security question answering: A security system for a product may ask questions that only the user knows the answer to. This can help verify a user’s identity when they log into an account. Examples of security question topics include the color of your first car or your mother’s maiden name.
Account locking: After a certain number of login attempts, a security system may lock an account to protect a user’s information from potential hackers. To unlock their account, a user can typically call the company to verify their identity and set a new password.
Portability means how effectively a system performs in one environment compared to another. For example, a user might purchase a new cell phone model and download a mobile application they had on their last device. If the application runs as efficiently on the new phone as it did on the old phone, then it’s highly portable. As a developer, you can design your applications to function properly on multiple devices to improve portability.
Highly compatible systems typically function well when other applications are running on a device. Compatibility also allows people who have different operating systems to use the same applications. For example, a compatible photo-sharing application may offer the same features on an iOS device as it does on an Android device. You can determine compatibility for a particular application by reading the product description, which may include operating system information.
The capacity of a system refers to the amount of storage it offers. When using some applications, users can adjust and save settings based on their preferences. For example, if you set your cell phone to vibrate when receiving incoming calls, the device typically records the change in settings. When a device has a high storage capacity, a user may personalize more settings or store large files such as lengthy documents or videos. Product labels typically express capacity in gigabytes or megabytes.
Technology that is highly reliable functions with the same or similar efficiency after extensive use. Here are three ways you can assess a device’s reliability:
Percentage of the probability of failure: You can check the percentage of the probability of failure, or failure rate, to determine the reliability of a system. If the percentage is higher, the system is likely to function normally after substantial use.
Number of critical failures: Consider recording the amount of critical failures a system experiences during testing to check its reliability. If the number of failures is low, it means that the system operates properly.
Time between critical failures: Tracking the time between critical failures can help you understand the reliability of a system. When critical failures occur rarely, it means that a system functions normally most of the time.
The environment includes external factors that impact how your system performs. For example, humid weather and exposure to water may affect the speed or reliability of an application. An application’s environment may also include the schedule on which it runs, such as 24 hours a day or only when the user launches it.
A localized application has features that match the geographical location of its users, including aspects such as:
Measurements, such as pounds vs. kilograms
Usability refers to the ability to use a particular product, including elements such as:
Navigation: When an application is usable, users can easily navigate its interface. For example, if a person navigates an effective user interface (UI) for a streaming service, they can understand how the application organizes its content and know where to access pages such as settings.
Purpose of features: With high usability, users can easily determine what a feature is and what it can do. For instance, they might predict that tapping a button with a picture of a magnifying glass may open a search bar.
Quality of performance: When a device performs well, it means that the features of a system are functioning well based on what a developer predicted. For example, if an application label states it can improve a cell phone’s battery life, the user may assess battery life over time to determine whether the product performed as expected.
Ways to evaluate nonfunctional requirements
You can evaluate the quality of your nonfunctional requirements in the following ways:
Assess user expectations. Think about what level of quality your target audience is seeking. For example, they may expect enhanced security options or high-speed performance. Meeting their expectations can help improve the public perception of your application’s performance.
Recognize the market demand. Consider conducting market research to determine the demand for specific nonfunctional requirements and comparing them to what your competitors already offer. Then you can innovate designs that other companies haven’t released yet, such as crack-resistant screens.
Analyze the performance. Try testing how your nonfunctional requirements work to assess their quality. You can gather a focus group to provide feedback on the usability or review the number of shutdowns to find out how quickly an application can overcome technical errors.
Best practices for nonfunctional requirements
You can follow these practices to maximize the performance of nonfunctional requirements:
Set clear expectations
Clear expectations for your nonfunctional requirements can enable you to:
Identify problems. Setting measurable goals can help you identify problems and test potential solutions. You can troubleshoot your product features to find out the strengths of the system and discover what you may need to work on next.
Save time and resources. Developing a clear strategy can help you understand which tasks to prioritize and determine what you want your final product to look like.
Market your product effectively. After testing your nonfunctional requirements, you can learn the capabilities and limitations of your products, which may enable you to emphasize the high-performing features in your marketing strategy.
Apply consistent formatting
Applications with consistent formatting can help establish your professional brand. For example, you might add a white search bar to the top of each application your company produces. Adding a consistent, distinct function to each of your products can help people identify your company as the creator. This may also encourage your customers to make purchases and increase brand loyalty.
Quantify your expectations
Quantifying how you want your nonfunctional requirements to perform can help you evaluate their successes. For instance, you might establish that you want your application to run at a particular speed. Then you can test how quickly it performs and identify how it can improve.
Prioritize the experience of the user
As you set performance standards for your product, it’s important to consider the perspective of the user. You can do this by finding a connection between the purpose of your product and customer expectations. For instance, if your customers are interested in a product that maintains the privacy of their messages and pictures, you might add nonfunctional features that enhance your application’s security.
Depending on your target audience, you may prioritize certain nonfunctional requirements over others. For example, if you’re producing a wearable device for athletes, you might consider the environmental factors they encounter during training, such as moisture and heat.
Use existing products as guides
If you’re developing an application that’s similar to a product already on the market, consider using the existing product as a guide. For example, if you’re designing a picture editing application, you might evaluate the features of similar systems to determine what nonfunctional requirements the developer applied. Then you can try implementing those features to make your application function more efficiently.
I hope you find this article helpful.