A SysML Profile for Fault Trees:Linking Safety Models to System Design

Model Based Systems Engineering (MBSE) has encouraged the use of a single systems model in languages such as SysML that fully specify the system and which form the basis of all development effort. However, using SysML models for safety analysis has been restricted by the lack of defined modelling standards for analytical techniques like Fault Tree Analysis (FTA). In lieu of such standards, the ENCASE project (See acknowledgements.) has formulated a simple SysML profile that captures the information required to represent fault trees and which enables the linkage of failure modes to other parts of the SysML model. We describe our experience of integrating fault tree models within a SysML MBSE environment for critical systems development, and show how that can be done while keeping existing (often certified) analytical tools as part of the development process. Common definitions of the system specification improves the quality of safety analysis, and the closer alignment of system and safety models provides opportunities for greater traceability, coherence and verification.