  This paper proposes a novel model-based approach to combine the quantitative
dependability (safety, reliability, availability, maintainability and IT
security) analysis and trade-off analysis. The proposed approach is called DPN
(Dependability Priority Numbers) and allows the comparison of different actual
dependability characteristics of a systems with its target values and evaluates
them regarding trade-off analysis criteria. Therefore, the target values of
system dependability characteristics are taken as requirements, while the
actual value of a specific system design are provided by quantitative and
qualitative dependability analysis (FHA, FMEA, FMEDA, of CFT-based FTA). The
DPN approach evaluates the fulfillment of individual target requirements and
perform trade-offs between analysis objectives. We present the workflow and
meta-model of the DPN approach, and illustrate our approach using a case study
on a brake warning contact system. Hence, we demonstrate how the model-based
DPNs improve system dependability by selecting the project crucial dependable
design alternatives or measures.
