The ISO 9126-1 specifies three models of software quality: internal, external and in-use. The models for internal and external quality are identical.

Internal and External Quality Models

  • Functionality
    • Suitability
    • Accuracy
    • Interoperability
    • Security
    • Functionality compliance
  • Reliability
    • Maturity
    • Fault tolerance
    • Recoverability
    • Reliability compliance
  • Usability
    • Understandability
    • Learnability
    • Operability
    • Attractiveness
    • Usability compliance
  • Efficiency
    • Time behavior
    • Resource utilization
    • Efficiency compliance
  • Maintainability
    • Analyzability
    • Changeability
    • Stability
    • Testability
    • Maintainability compliance
  • Portability
    • Adaptability
    • Installability
    • Coexistence
    • Replaceability
    • Portability compliance

In-use Quality Model

  • Effectiveness
  • Productivity
  • Safety
  • Satisfaction