Architecting Dynamic Reconfiguration in Dependable Systems

The need for dynamic reconfiguration is a complicating factor in the design of dependable systems, as it demands from software architects both rigour and planning. Although recent research has shown that systematic and integrated “specification-to-deployment” environments are promising approaches to architecting dependable systems, few proposals have yet considered dynamic reconfiguration, and then only in specific situations. In this paper, we propose a generic approach to supporting dynamic reconfiguration in dependable systems. The proposed approach is built on our view that dynamic reconfiguration in such systems needs to be causally connected

at runtime

to a corresponding high-level software architecture specification. In more detail, we propose two causally-connected models: an architecture-level model and a runtime-level model. Dynamic reconfiguration can be applied either through an architecture specification at the architecture level, or through reconfiguration primitives at the runtime level. Both foreseen and unforeseen reconfigurations are supported. We discuss the issues involved in handling these two types of reconfiguration at both levels and the mapping between them. We also discuss an implementation of our approach that evaluates its main benefits.