A Self-Optimizing Run-Time Architecture for Configurable Dependability of Services

Many human activities today depend critically on systems where substantial functionality has been realized using complex software. Therefore, appropriate means to achieve a sufficient degree for dependability are required, which use the available information about the software components and the system architecture. For the special case of service-based architectures,ext-- an architecture proposed to cope with the complexity and dynamics of today's systems -- we identify in this paper a set of architectural principles which can be used to improve dependability. We then describe how the identified architectural principles have been used in a realized service-based architecture which extends Jini. The dependable operation of the infrastructure services of the architecture further enables to systematically control and configure some dependability attributes of application services. We present a qualitative and quantitative evaluation of the dependability for a configuration of multiple identical services which are executed with the architecture and show how the different parameters effect the dependability. Additionally, a scheme for the dynamic control of the required dependability of the application services in the case of changing failure characteristics of the environment is outlined. Finally, we present a first evaluation of the developed architecture and its dynamic control of dependability.