Understanding Preconditions in STAMP/STPA Analysis

  • The first step in STAMP/STPA analysis involves defining the analysis purpose and determining preconditions and assumptions.
  • While it’s not mandatory to establish preconditions initially, developing at least the minimum necessary preconditions is advisable. Insufficient preconditions can lead to an unwieldy number of Unsafe Control Actions (UCA), hindering effective analysis.
  • Preconditions can serve multiple purposes, such as:
    • Complementing original requirement specifications.
    • Providing additional requirements for subsequent development.
    • Defining the scope of the analysis.
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Defining Preconditions in Astah

Precondition tables in Astah are created in a tabular format.

  1. To start, navigate to [Diagram] → [STAMP/STPA] → [Precondition Table].

  2. Select [File] → [New].
  3. Open the [STPA Procedure] tab in the top-left pane and double-click on [Determine Precondition].
  4. A blank Precondition table will open.
    STPA Precondition Table

  5. Right-click on the table and choose [Add Precondition] from the context menu. Add STPA Precondition

  6. A new line will appear for you to directly input the precondition.STPA-Preconditions

Note: For changing the font style in the table, refer to the ‘Change Font‘ section of this guide.