Dynamic Adaptation of Dependable Systems

Dependable software systems, like any other software sys-tem, are subject to change during their lifetimes. Tradi-tional approaches to bringing about change require that the system be brought offline temporarily. However, this is often undesirable due to requirements for high avail-ability. Furthermore, dramatically reducing availability may also cause a reduction in other dependability at-tributes such as security, safety and reliability. This pa-per presents an overview of a framework for managing change in dependable systems dynamically with the aim of preserving a high degree of availability. The framework allows the dynamic change process, controlled by an open set of algorithms, to be monitored and the impact of par-ticular algorithms on a system’s dependability attributes to be revealed. Novel aspects of our work include support for making an informed decision about the algorithm used to control the change process and the means to assess the dependability of change control algorithms.