[STPA] Loss Hazard Safety Constraint Table

The Loss Hazard Safety Constraint Table is a pivotal component in STPA (System-Theoretic Process Analysis) for defining specific losses that your system aims to prevent. This table facilitates the identification of hazards—specific system states or conditions posing a risk of loss. It also serves to establish safety constraints, which are measures or conditions required to mitigate identified hazards. This step is critical for delineating the system’s safety requirements and strategies for risk reduction.

Creating a Loss Hazard Safety Constraint Table

Navigate to [Diagram] → [STAMP/STPA] → [Loss Hazard Safety Constraint Table].


Alternatively:
1. Go to [File] → [New].
2. Select the [STPA Procedure] tab, double-click on [Identify Loss, Hazard, Safety Constraint].

Adding Losses

To insert a loss, right-click on the table and select [Add Loss].

Adding Hazards

Once a loss is listed, associate hazards that could lead to this loss. Right-click on the [Loss] field and select [Add Loss].

To link a hazard to multiple losses, use the [Add Existing Hazard] dropdown list to attach an existing hazard.

Adding Safety Constraints

For defining safety constraints associated with a loss and its hazard, right-click on the [Safety Constraint] field and choose [Add Safety Constraint].

If a safety constraint applies to several hazards, select it from the [Add Existing Safety Constraint] dropdown list.

Managing Automatic ID Assignment

By default, Astah assigns IDs (e.g., L1, L2 for Losses; H1, H2 for Hazards) automatically.
To edit these IDs, double-click on them.


To disable automatic ID assignment:

1. Go to [Tools] → [System Properties].
2. In the [System Properties] window, select [Other] under [STAMP/STPA].
3. Uncheck [Automatically Assign IDs] and click [Apply] → [OK].
   
   
   Note: Disabling this feature will also stop auto-ID creation for other elements like Preconditions and Countermeasures.