ALFRED: A Methodology to Enable Component Fault Trees for Layered Architectures

Abstract

Identifying drawbacks or insufficiencies in terms of safety is important also in early development stages of safety critical systems. In industry, development artefacts such as components or units, are often reused from existing artefacts to save time and costs. When development artefacts are reused, their existing safety analysis models are an important input for an early safety assessment for the new system, since they already provide a valid model. Component fault trees support such reuse strategies by a compositional horizontal approach. But current development strategies do not only divide systems horizontally, e.g., by encapsulating different functionality into separate components and hierarchies of components, but also vertically, e.g. into software and hardware architecture layers. Current safety analysis methodologies, such as component fault trees, do not support such vertical layers. Therefore, we present here a methodology that is able to divide safety analysis models into different layers of a systems architecture. We use so called Architecture Layer Failure Dependencies to enable component fault trees on different layers of an architecture. These dependencies are then used to generate safety evidence for the entire system and over all different architecture layers. A case study applies the approach to hardware and software layers.

Improved Safety Analysis Integration in a Systems Engineering Approach

“…Concerning the generation of the fault trees from system models, we cite some works that allow the generation of the static and dynamic fault trees from system structure. The related work is divided into two categories: works that do not consider the redundancy in the generation of fault trees such as [19][20][21][22][23][24] and others that consider the redundancy during the generation of fault trees such as [25][26][27][28][29].…”

Towards the Adoption of Model-Based Engineering for the Development of Safety-Critical Systems in Industrial Practice

“…Hence, it is possible to construct a safety analysis model based on the reuse of preexisting parts and the specification of the newly created parts (compositional safety assessment). In terms of top-down safety analysis, one possible direction is to use the CFT methodology and to establish a framework to synchronize with the system design model and to store and exchange specific CFT elements [17]. Another direction is to enable reuse in bottom-up safety analysis, e.g.…”

Towards Continuous Safety Assessment in Context of DevOps

“…The paper is concluded in Sec. 7 2 Related Work R-Scrum [2] and SafeScrum [5] are existing approaches to develop safety-critical systems using agile methods, but do not show how to build a continuous delivery pipeline. Also [22] only presents challenges how to enable agile development of safety-critical systems in large organizations.…”