SAHRA (STPA based Hazard and Risk Analysis) as a software tool for STAMP/STPA improves the analysis workflow by not only supporting the complete STPA process but by also offering a unique way to capture Step 1 and 2 using the visual style of mind maps. SAHRA is seamlessly integrated into the widely used UML solution Sparx Systems Enterprise Architect (EA). This integration enables synergies between design of a system and its safety analysis and thus allows to use STPA in the paradigm of safety-guided design

Hilbes, Christian

Krauss, Sven Stefan

Rejzek, Martin

Senn, Christoph

ZHAW digitalcollection

Sven S. Krauss, Martin Rejzek, Christoph W. Senn, Christian HilbesInstitute of Applied Mathematics and Physics IAMPZurich University of Applied Sciences ZHAW, Switzerlandwww.sahra.chwww.zhaw.ch/iamp/sksSAHRA (STPA based Hazard and Risk Analysis) as a software tool for STAMP/STPA improves the analysis work-flow by not only supporting the complete STPA process but by also offering a unique way to capture Step 1 and 2 using the visual style of mind maps. SAHRA is seamlessly integrated into the widely used UML solution Sparx Systems Enterprise Architect (EA). This integration enables synergies between design of a system and its safety analysis and thus allows to use STPA in the paradigm of safety-guided design.Screenshot of SAHRA as extension for the UML/SysML tool Enterpri-se Architect. The model of a Hierarchical Control Structure is shown in the center of the screenshot. The controller ‘Central control unit’ is currently selected. The toolbox (top left) contains all elements needed for capturing STPA diagrams. The model repository and its structure is shown in the repository tree (right).Capturing the Hierarchical Control StructureWe consider hierarchical control structures (HCS) as just ‘another view’ of a system. SAHRA allows to cap-ture HCS as diagrams and stores all information,  to-gether with design data in a common database, the so called model repository.SAHRA’s context sensitive object browser shows information for  the currently selected element: controller (left), control action connector (center), control action (top right), hazard (bottom right).A Unique Style of AnalysisA tendency of the wide spread approach to document STPA Step 1 using tables is to omit details as there is only very limited space for writing them down and to maintain consistency as relationships need to be maintained by hand. SAHRA therefore introduces mind maps, as means of visually representing and editing an analysis. This enables the analyst to see relations-hips at a glance and provides maximal flexibility with respect to documentation details.STPA step 2 control loops can be captured just as hierarchical control structures.ResultsSAHRA has been successfully used in the context of applied research and development projects in indus-try and academia. The innovative approach using a directed graph and its visual representation as mind map proved SAHRA‘s capability to analyze large and complex systems.SAHRA allows to capture STPA Step 1 and 2 analysis in the visual style of mind map diagrams. The analysis information is captured by individual elements reflecting for example Keywords, UCAs, Hazards, and Losses. This provides maximum flexibility to the analyst in terms of documenting the analysis. Drag and drop from the lower left panel allows to easily create new elements. Drag and drop from the lower right panel allows to reuse existing elements while inheriting existing relationships.SAHRA Object Browser for TraceabilityThe information of the mind maps is used to build a di-rected graph in the model repository serving as foun-dation for traceability analysis. To support the analyst, SAHRA provides a context sensitive object browser. Integration AdvantagesSAHRA is integrated into EA which enables the user to fully benefit from already existing EA features like multi-user support, scripting, automation, and confi-guration management integration. These features are extended by providing a dedicated STPA profile, inclu-ding diagram types, elements and toolboxes for STPA modelling. SAHRA comes with a set of templates to generate customizable documents, reports and se-arch queries.Requirements, Design & Analysis in One RepositoryAll elements created with SAHRA are stored in a com-mon model repository. This allows to easily reuse them in other diagrams and to establish relationships bet-ween requirements, design, and safety analysis.AcknowledgementsThe project is funded by the Swiss Commission for Technology and Innovation(CTI, 15822.1 PFIW-IW) and by Curtiss-Wright Drive Technology GmbH. ReferencesSparx Systems Pty Ltd. http://www.sparxsystems.comThomas, J. (2013). Phd Thesis, MIT Boston USASAHRA - An integrated software tool for STPAToolboxElements and structure of the model repositoryDrawing canvascreate new elementreuse existing element

SAHRA - an integrated software tool for STPA

ZHAW Zürcher Hochschule für Angewandte Wissenschaften

https://digitalcollection.zhaw.ch/bitstream/11475/13635/3/2016_Krauss_SAHRA_an_integrated_software_tool_for_STPA.pdf

SAHRA - an integrated software tool for STPA

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