Standards families
Fault tree and event tree
Top-down fault logic (AND/OR gates to basic events) and the forward event tree from an initiating event through safety functions.
fault.tree@1New DDN source
Why use it?
Safety arguments must be enumerable: every path to the hazard drawn, every barrier after the initiator named.
When it helps
Hazard analysis, reliability reviews, safety-case documentation.
How to read it
- Fault tree: read downward from the top event through gates to basic events; AND gates need all inputs, OR needs one.
- Event tree variant: read left to right — each branch point is a safety function succeeding or failing.
What you need
- The top event / initiating event
- The gates and basic events
- The safety functions
Things to check
- Do not hide a common cause in two "independent" branches.
- A basic event with no failure rate is a placeholder — mark it as one.
Scope of this diagram
Declared trees with gate-logic validation; probability quantification is out of scope unless declared.
Work with the converted example
- Open the viewer and select
fault. Inspect the rendered view and its source. - Open the designer. Keep the selected profile and inspect its legal palette and property controls.
- Change one displayed title or an appropriate data value. Apply the edit and check the resulting diagram.
- Run the verifier and review its diagnostics before moving complete content into review.
- Download your edited DDN source to retain the change.
The example uses the indentation-based ddn-next-1 dialect. The language guide explains reusable definitions, dotted data rows and explicit property blocks.