STAMP/STPA and SCDL Diagrams
Astah System Safety supports the following diagrams for SCDL and STAMP/STPA.
Safety Concept Diagram
Safety Concept Diagram is a structure diagram to represent architecture of the functional safety that is formed by Safety Concept Notation Study Group. It visualizes interactions between requirements, allocations between elements and requirements, and you can add the “weight” properties to decompositions.
This is a similar diagram to Function Block Diagram (FBD), so that it can be widely used not limited to ISO 26262.User Guide
Accident Hazard Safety Constraint Table
Accident Hazard Safety Constraint Table is also what you use at STEP1 of STPA analysis to define the accidents and losses that you want the system to prevent throughout this analysis, and identify hazards – system state or set of conditions that will lead to a loss and the safety constraints.
Control Structure Diagram
Control Structure Diagram is what you use at STEP2 of STPA analysis to construct and visualize the control structure and relationships between the Components.
UCA (Unsafe Control Action) Table
The UCA (Unsafe Control Action) table is what you use at STEP3 of STPA analysis to identify unsafe control actions. When you create a UCA table, Astah automatically lists up all the control actions you defined in the Control Structure Diagram and puts them in a table.
Control Loop Diagram
Control Loop Diagram is what you use at STEP4 of STPA analysis. This diagram shows a control loop with actions and feedback. By creating a control loop diagram of “Unsafe Control Actions”, it will help you identify the hazard causal factors.
The Countermeasure Table is where you identify the countermeasures for all the scenarios you created throughout the STPA analysis. This table will help you make sure that countermeasures you have created for specific scenarios are aligned and do not contradict to the system as a whole.