Design of Self-Managing Dependable Systems with UML and Fault Tolerance Patterns

The development of dependable software systems is a costly un-dertaking. Fault tolerance techniques as well as self-repair capa-bilities usually result in additional system complexity which can even spoil the intended improvement with respect to dependabil-ity. We therefore present a pattern-based approach for the design of service-based systems which enables self-managing capabilities by reusing proven fault tolerance techniques in form of Fault Toler-ance Patterns. The pattern specification consists of a service-based architectural design and deployment restrictions in form of UML deployment diagrams for the different architectural services. The architectural design is reused when designing the system architec-ture. The deployment restrictions are employed to determine valid deployment scenarios for an application. During run-time the same restrictions are at first used to automatically map additional ser-vices on suitable nodes. If node crashes are detected, we secondly employ the restrictions to guide the self-repair of the system in such a way that only suitable repair decisions are made. 1