When it comes to software development, there are two types of requirements: functional and non-functional. While functional requirements describe what the software should do, non-functional requirements describe how well the software should do it. In other words, non-functional requirements define the performance, usability, security, and other qualities of the software. In this article, we will explore non-functional requirements examples and how they contribute to the success of a software project.

What are Non-Functional Requirements?

Non-functional requirements, also known as quality or performance requirements, define the attributes of the software system that are not related to its functionality. Non-functional requirements include the following:

• Performance: This refers to the speed, throughput, and response time of the software system. It includes factors such as latency, throughput, and response time.
• Usability: This refers to the ease of use, learnability, and user experience of the software system. It includes factors such as accessibility, user interface design, and user satisfaction.
• Security: This refers to the confidentiality, integrity, and availability of the software system. It includes factors such as authentication, authorization, and encryption.
• Reliability: This refers to the availability, fault tolerance, and recoverability of the software system. It includes factors such as uptime, mean time between failures (MTBF), and mean time to repair (MTTR).
• Maintainability: This refers to the ease of maintenance, modification, and adaptability of the software system. It includes factors such as code readability, documentation, and testability.

Examples of Non-Functional Requirements

To better understand non-functional requirements, let us look at some examples:

Performance

• The system should respond to a user’s request within 3 seconds.
• The system should handle 1000 concurrent users without degrading performance.
• The system should process 100 transactions per second.

Usability

• The system should be accessible to users with disabilities.
• The system should have a user interface that is intuitive and easy to use.
• The system should provide helpful error messages and clear feedback to the user.

Security

• The system should use SSL encryption for all communications.
• The system should have a strong password policy.
• The system should have authentication and authorization mechanisms.

Reliability

• The system should have a mean time between failures (MTBF) of at least 10,000 hours.
• The system should be able to recover from failures within 5 minutes (mean time to repair or MTTR).
• The system should have a backup and recovery plan in place.

Maintainability

• The system should have clear and concise documentation.
• The system should have a modular and well-organized code structure.
• The system should have unit tests and integration tests.

Importance of Non-Functional Requirements

Non-functional requirements are critical to the success of a software project. Without them, software systems may not perform as expected, may be difficult to use, may be insecure, may be unreliable, and may be difficult to maintain. Non-functional requirements help ensure that software systems meet the needs of users, stakeholders, and the business.

Non-functional requirements also help developers make design decisions. For example, if a system must support 1000 concurrent users, the developer may choose a distributed architecture that can scale horizontally. If a system must be accessible to users with disabilities, the developer may choose a user interface that supports screen readers and keyboard navigation.

Furthermore, non-functional requirements help ensure that software systems meet industry standards and regulations. For example, if a system processes financial transactions, it must comply with PCI-DSS (Payment Card Industry Data Security Standard) requirements.

FAQs

What is the difference between functional and non-functional requirements?

Functional requirements describe what the software should do, while non-functional requirements describe how well the software should do it. Functional requirements are concerned with the behavior and features of the software, while non-functional requirements are concerned with the performance, usability, security, reliability, and maintainability of the software.

Why are non-functional requirements important?

Non-functional requirements are important because they help ensure that software systems meet the needs of users, stakeholders, and the business. They also help developers make design decisions and ensure that software systems meet industry standards and regulations.

How do you define non-functional requirements?

Non-functional requirements can be defined by analyzing the needs of users, stakeholders, and the business. They can also be defined by considering industry standards and regulations, as well as best practices in software development.

How do you test non-functional requirements?

Non-functional requirements can be tested using various methods, such as performance testing, usability testing, security testing, reliability testing, and maintainability testing. These tests can be automated or manual, and can involve simulating different scenarios and user behaviors.

Can non-functional requirements change during a project?

Yes, non-functional requirements can change during a project. This can happen due to changes in user needs, stakeholder requirements, or business goals. It is important to manage these changes effectively and ensure that they do not negatively impact the project schedule or budget.

Conclusion

Non-functional requirements are essential to the success of a software project. They define the performance, usability, security, reliability, and maintainability of the software system, and help ensure that it meets the needs of users, stakeholders, and the business. By considering non-functional requirements early in the software development life cycle, developers can make informed design decisions and deliver software systems that meet industry standards and regulations.