The role of independent verification and validation in maintaining a safety critical evolutionary software in a complex environment: the NASA Space Shuttle program

The National Aeronautics and Space Administration (NASA) Space Shuttle program is a multi-billion dollar activity scheduled to span over 40 years. Maintaining such software with requirements for high reliability and mission safety taxes current development methods. The authors present how independent verification and validation (IV&V) activities are used to support these requirements. They also show how the IV&V activities for this program differ from those of more traditional software developments.