Being trustworthy or performing consistently well.


Capability of a product to perform specified functions under specified conditions for a specified period of time without interruptions and failures.

Note: Wear does not occur in software. Limitations in reliability are due to results from faults in requirements, design and implementation, or from contextual changes.”

ISO-25010:2023


Typical Acceptance Criteria

  • Time or time interval when the system shall be available
  • Availability percentage
  • Time to detect a fault
  • Time to repair a fault
  • Time or time interval in which the system may operate in degraded mode
  • Proportion (e.g. 99%) or rate (e.g. up to 42 per second) of a certain class or types of faults that the system either prevents or handles without failing

Source: Bass et al., 2021, p. 75

What Stakeholders mean by reliable

Stakeholder (potential) Expectation for reliable
User * available when need it
* produces expected results
* offers expected functionality
* user documentation is reliable
Product-Owner * realiably add new functions and features
* reliable estimates concerning effort for changes
* reliable at runtime, available when users need it
Management * cost and effort of development, operations and support are reliably predictable
* reliable with respect to operations, especially security and interoperability
Developer * reliably add new features or functions to the system without unwanted side-effects.
* realiably predict the effects of changes to the system
Tester test results are reliable (as in consistent or repeatable)
Admin * reliably start, configure and monitor the system
* reliable release and update processes
Domain-Expert -
Others * technical documentation is reliable (current and correct)

Qualities tagged with #reliable

Requirements tagged with #reliable