What is an example of a reliability non-functional requirement?

Reliability is a critical non-functional requirement that ensures a system operates consistently and performs its required functions under stated conditions for a specified period. It encompasses various aspects such as system uptime, error handling, and the system's ability to recover from failures without loss of data or functionality.

Example of a Reliability Non-Functional Requirement

Context: Consider an online banking system where users expect to access their accounts, perform transactions, and use various banking services without interruptions.

Reliability Requirement:

• Availability: The online banking system must be operational and available to users 99.99% of the time, 24/7, excluding scheduled maintenance windows. This availability is crucial because it ensures that users can rely on the system to be up and running whenever they need to access their financial information or perform transactions.

• Failover Capability: In the event of a system failure, the system must automatically switch to a redundant backup system within 1 minute to ensure continuous service availability. This failover process should be seamless to the user, preventing any interruption in service.

• Data Integrity: All financial transactions must be processed correctly and reliably, with full assurance that no transaction data is lost or corrupted. The system must implement transaction logs and rollback capabilities to ensure that all operations can be audited and, if necessary, undone to maintain data integrity.

• Error Handling: The system must gracefully handle errors without causing system crashes or data loss. User-friendly error messages should be provided to inform users of what went wrong and the next steps, if any, they should take. For example, if a transaction fails due to a network issue, the system should inform the user of the failure and offer the option to retry the transaction.

Importance of This Requirement

The reliability of the online banking system directly impacts user trust and satisfaction. Users expect their banking operations to be available and accurate without any risks of errors or downtime that could affect their financial activities. Ensuring high reliability also helps the financial institution maintain regulatory compliance and protect its reputation.

Measuring Reliability

To ensure that the reliability requirements are met, the system must be regularly tested and monitored:

• Performance Monitoring: Continuously monitor system performance and availability using tools that can alert administrators about potential downtimes or performance degradations.
• Regular Testing: Perform regular stress testing and failover tests to ensure the system can handle real-world operational loads and smoothly transition to backup systems without user disruption.
• Audit and Logging: Implement comprehensive logging and audit trails that help in diagnosing issues, understanding system failures, and improving system reliability over time.

Conclusion

Defining and implementing reliability as a non-functional requirement involves detailed planning around system availability, robust error handling, data integrity, and recovery mechanisms. This ensures the system can reliably meet user expectations and operational demands, which is essential for maintaining service quality and user trust, especially in critical applications like online banking.