Dependability through Assured Reconfiguration in Embedded System Software

In many software systems, properties necessary for dependable operation are only a small subset of all desirable system properties. Assuring properties over the simpler subset can provide assurance of critical properties over the entire system. This work provides a method for constructing systems to be dependably reconfigurable. A system´s primary function can have less demanding dependability requirements than the overall system because the system can reconfigure to some simpler function. Reconfiguration thus controls the effective complexity of the system without forcing that system to sacrifice desired, but unassurable, capabilities. Focusing a system´s dependability argument on reconfiguration means that reconfiguration must proceed correctly with very high assurance. The system construction approach in this work also provides a method through which system dependability properties can be shown. To illustrate the ideas in this work, we have built part of a hypothetical avionics system that is typical of what might be found on an unmanned aerial vehicle