Implementing Mixed Criticality Systems in Ada

Many safety-critical embedded systems are subject to certification requirements. However, only a subset of the functionality of the system may be safety-critical and hence subject to certification; the rest of the functionality is non safety-critical and does not need to be certified, or is certified to a lower level. The resulting mixed criticality system offers challenges both for static schedulability analysis and run-time monitoring. This paper considers both of these issues and indicates how mixed criticality applications can be implemented in Ada. In particular, code is produced to illustrate how the necessary run-time mode changes can be supported. This support makes use of a number of the new features introduced into Ada 2005.