What are the valid non-functional requirements?

Valid non-functional requirements (NFRs) are those that effectively define how a system should operate, focusing on its performance and quality attributes rather than its specific functionalities. These requirements are crucial because they directly impact the user experience, system reliability, performance, and overall satisfaction. Here’s a breakdown of various categories and examples of valid non-functional requirements that are commonly specified in system design:

1. Performance

• Response Time: The system should respond to user queries within 2 seconds.
• Throughput: The system must handle 100 transactions per second.
• Capacity: The system should support up to 10,000 concurrent users.

2. Scalability

• Scalability: The system should scale horizontally by adding more servers to handle increases in load without significant degradation in performance.
• Load Balancing: The system must distribute incoming requests evenly across multiple servers.

3. Reliability

• Availability: The system should be up and running 99.9% of the time.
• Recovery: The system must recover from a major failure within 1 hour without data loss.
• Fault Tolerance: The system should continue to operate close to normal levels even if one of the components fails.

4. Usability

• Accessibility: The system must comply with the WCAG 2.1 AA standards for accessibility.
• User Experience: Interfaces should be intuitive and require minimal training for new users.

5. Maintainability

• Modifiability: Updates and modifications to the system should be deployable without significant downtime.
• Testability: The system should be designed to easily allow the execution of automated tests to check its performance and behavior.

6. Security

• Data Encryption: Sensitive data must be encrypted in transit and at rest using industry-standard encryption methods.
• Authentication and Authorization: The system must support multifactor authentication and role-based access control.

7. Compliance

• Regulatory Compliance: The system must meet specific standards and regulations, such as GDPR for data protection or HIPAA for healthcare systems.
• Standards Compliance: The system must adhere to specific industry standards, such as ISO/IEC 27001 for information security management.

8. Portability

• Platform Independence: The system should be operable on both Windows and macOS without requiring modification.
• Interoperability: The system must be able to exchange data with other systems using standardized protocols.

9. Disaster Recovery

• Backup: The system must perform nightly backups of all data, which must be stored in a geographically separate location.
• Recovery Time Objective (RTO): The system should be fully operational within 4 hours after any disaster recovery activation.

10. Operational

• Serviceability: The system should be easy to diagnose and repair.
• Environmental: The system should comply with environmental standards, such as energy consumption limits or operation under specific environmental conditions.

How to Ensure Non-Functional Requirements are Valid

To ensure that non-functional requirements are valid and effective, they should be:

• Specific: Clearly define the expected standard or threshold.
• Measurable: Quantify the requirements so that their implementation can be verified.
• Achievable: Realistically attainable given the project constraints and technology.
• Relevant: Directly related to the business or operational goals of the system.
• Time-bound: Include time frames where applicable (e.g., recovery times).

Non-functional requirements play a vital role in the system's architecture by defining criteria that ensure the system's utility, efficiency, and effectiveness. They need careful consideration and clear articulation to ensure the system meets the broader business and user needs.