When it comes to designing a robust and user-friendly system, understanding the difference between functional and non-functional requirements is crucial. These two types of requirements play distinct roles in shaping a system, and both are essential for creating a product that meets user needs and performs effectively in real-world scenarios. In this blog post, we’ll delve into these requirements using a real-world example to illustrate their importance and interplay.
Functional Requirements: The “What”
Functional requirements define what a system is supposed to do. They lay out the specific behaviors or functions of a system and are typically centered around user actions and system responses. Think of functional requirements as the “verbs” of your system—they describe actions and interactions.
Imagine you’re designing a WhatsApp messenger system. The functional requirements might include:
- Sending and Receiving Messages
- Multimedia Sharing
- Voice and Video Calls
- Contact Management
- Group Chats
- Status Updates
- Notifications
Let’s understand this functional requirement in detail:
Sending and Receiving Messages: Users must be able to send text messages to their contacts and Users must receive text messages in real-time.
Multimedia Sharing: Users should be able to send and receive images, videos, and voice notes.
Voice and Video Calls: Users should be able to make voice calls and video calls to their contacts and receive voice calls and video calls from their contacts.
Contact Management: Users should be able to add new contacts or remove existing ones and The app should synchronize with the phone’s contact list.
Group Chats: Users should be able to create group chats with multiple contacts and be able to send and receive messages in group chats.
Status Updates: Users should be able to post status updates (text, photo, video) visible to their contacts and be able to able to view status updates posted by their contacts.
Notifications: Users should receive real-time notifications for new messages, calls, and status updates.
Non-Functional Requirements: The “How”
Non-functional requirements, on the other hand, describe how a system performs a function. These requirements define the system’s operational attributes, such as performance, security, usability, and reliability. Non-functional requirements are often considered the “adjectives” of your system—they describe qualities and characteristics.
For WhatsApp, important non-functional requirements include:
- Performance
- Scalability
- Security
- Reliability
- Usability
- Battery Efficiency
- Localization
Let’s understand this non-functional requirement in detail:
Performance: Messages should be sent and received within milliseconds to ensure real-time communication and the app should load quickly and respond to user actions without delays.
Scalability: The system should support millions of concurrent users without performance degradation and backend infrastructure should efficiently distribute the load to handle peak usage times.
Security: All messages and calls should be end-to-end encrypted to ensure user privacy and user data should be securely stored and protected from unauthorized access.
Reliability: The app should be available 99.99% of the time, ensuring users can always connect and system should gracefully handle errors and recover without data loss.
Usability: The app should have an intuitive and easy-to-navigate interface and app should be accessible to users with disabilities, including screen readers and other assistive technologies
Battery Efficiency: The app should be optimized to minimize battery usage, allowing users to stay connected for longer periods.
Localization: The app should support multiple languages to cater to a global user base and app should adapt to different cultural norms and preferences
Conclusion
In summary, functional requirements define what a system should do, while non-functional requirements describe how the system should perform those functions. Both are vital in system design, ensuring that the end product is not only capable of performing necessary tasks but also doing so in a manner that meets performance, security, and usability standards. By carefully considering and balancing these requirements, designers can create systems that are both effective and efficient, providing a seamless and satisfactory user experience.
Next time you use WhatsApp or any other app, remember the intricate dance between these requirements that makes your experience smooth and enjoyable.