Safety-Critical systems, as used in the automotive, avionics, or aerospace domains, are becoming increasingly software-reliant to the extent that the system cannot function without the software. On one hand the software system provides an integrated set of functionality to operate the system and manage failure and unsafe conditions. Current best safety engineering practices, such as DO178B/C or SAE ARP4761, are labor intensive and are only performed as part of the system engineering process. At the same time increased interaction complexity of the embedded software with the hardware platform and mechanical system has resulted in the software to be a major source of defects with potentially fatal consequences.To address these issues, the SAE Architecture Analysis & Design Language (AADL) standard has been extended with an Error Model Annex to support architecture fault modeling and automated safety analysis. In this paper we introduce the concepts of the revised Error Model (EMV2) Annex and a fault propagation ontology to support such architecture fault models at three levels of abstraction focusing on fault propagation, failure behavior of individual components, and composite failure behavior of a system in terms of its components. Such specifications reflect fault tolerance strategies assumptions made by fault impact, fault tree and reliability analysis about the safety system component. We illustrate their use on a dual redundant flight guidance system and discuss the automation of different safety analysis methods in use by the SAE ARP4761, emphasizing on automation benefits.

Safety-critical systems are widely used in different domains and lead to an increasing complexity. Such systems rely on specific services such space and time isolation as in the ARINC653 avionics standard. Their criticality requires a carefully driven design based on an appropriate development process and dedicated tools to detect and avoid problems as early as possible.Model Driven Engineering (MDE) approaches are now considered as valuable approach for building safety-critical systems. The Architecture Analysis and Design Language (AADL) proposes a component-based language suitable to operate MDE that fits with safety-critical systems needs. This paper presents an approach for the modeling, verification and implementation of ARINC653 systems using AADL. It details a modeling approach exploiting the new features of AADL version 2 for the design of ARINC653 architectures. It also proposes modeling patterns to represent other safety mechanisms such as the use of Ravenscar for critical applications. This approach is fully backed by tools with Ocarina (AADL toolsuite), POK (AADL/AR-INC653 runtime) and Cheddar (scheduling verification). Thus, it assists system engineers to simulate and validate non functional requirements such as scheduling or resources dimensioning.

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