Safety Annex for the Architecture Analysis and Design Language

Abstract

Model-based development techniques are increasingly being used in the development of critical systems software. Leveraging the artifacts from model based development in the safety analysis process would be highly desirable to provide accurate analysis and enable cost savings. In particular, architectural and behavioral models provide rich information about the system's operation. In this paper we describe an extension to the Architecture Analysis and Design Language (AADL) developed to allow a rich modeling of a system under failure conditions. This emph{Safety Annex} allows the independent modeling of component failure modes and allows safety engineers to weave various types of faults into the nominal system model. The accompanying tool support allows investigation of the propagation of errors from their source to their effect on top level safety properties without the need to add separate propagation specifications; it also supports describing dependent faults that are not captured through the behavioral models, e.g., failures correlated due to the physical structure of the system. We describe the Safety Annex, illustrate its use with a representative example, and discuss and demonstrate the tool support enabling an analyst to investigate the system behavior under failure conditions.