Improvement of Dependability of Complex Web Based Systems by Service Reconfiguration

Web based information systems are exposed to various dependability issues during their lifetime (originating in the hardware, in the software or stemming from security vulnerabilities). We present an approach to use reconfiguration to circumvent these issues. The presentation is focused on the potential threads, measuring the dependability risks, constructing of optimal reconfiguration strategies and assessing their impact on the over-all dependability. The proposed technique involves construction of the reconfiguration graph, assessment of the steady state probabilities of web system dependability states and choosing the optimal strategy from among the admissible ones.