Bow-tie node and relationship types
Every node type and relationship type a bow-tie recognises, what to write for each, how each is drawn, and how the visual decides which side of the top event a node is on.
Node types
| Node type | Write it as | Drawn as | Role |
|---|---|---|---|
| Hazard | Hazard, HAZ | Orange hexagon above the top event | What causes harm once control of it is lost. One per bow-tie, connected to the top event. |
| Threat | Threat, Cause | Red triangle, far left | Something that can bring about the top event. |
| Preventive barrier | Preventive Barrier, Preventive, Prevention, Preventive Control | Blue rounded rectangle | Stops a threat reaching the top event. |
| Barrier | Barrier, Control, Safeguard, Measure, Defence, Defense, Protection, Protective Measure, Control Measure | Grey rounded rectangle, only when its side cannot be found | A barrier recorded without its side. It becomes preventive or recovery by where it sits. |
| Top event | Top Event, Top, TE, Loss of Control | Red diamond in the centre | The point where control is lost. One per bow-tie. |
| Mitigative barrier | Mitigative Barrier, Mitigative, Mitigation, Mitigative Control, Mitigation Measure, Recovery, Recovery Barrier, Recovery Control, Recovery Measure | Green rounded rectangle | Limits a consequence once the top event has happened. |
| Consequence | Consequence, Outcome | Pink parallelogram, far right | A result of the top event. |
| Escalation factor | Escalation Factor, Escalation | Amber dashed ellipse | A condition that weakens a barrier. |
| Escalation-factor control | Escalation Factor Control, Escalation Control, EFC | Grey dashed pill | Manages an escalation factor. |
Mitigative barriers are called recovery barriers in the summary strip and the Node Inspector. They are the same thing.
Matching ignores case, spaces, underscores, hyphens and full stops, so PreventiveBarrier, preventive_barrier and Preventive-Barrier all read as a preventive barrier. Wording that matches nothing can be mapped under Node type values on the Data Mapping tab. Colours, symbols and display names can be changed under Appearance → Node types.
Which side a node is on
The side comes from the connections, not the node type. A node on a path into the top event is on the threat side, and a node on a path out of it is on the consequence side. A barrier written as Barrier or Control takes the side it is found on.
When the type and the position disagree, the position is believed and the node is reported: a preventive barrier on the consequence side, a mitigative barrier on the threat side, a threat on the consequence side and a consequence on the threat side are all errors.
Relationship types
| Relationship type | Write it as | Use it for | Connector |
|---|---|---|---|
| Leads to | Leads To, Causes, Hazard to Top Event, Hazard Path, Releases | Any step on a path, and the hazard's connection to the top event. The default for a blank cell. | Grey arrow |
| Threat path | Threat Path, Preventive Path, Prevention Path, Preventive, Threat to Top Event, Barrier Path, Preventive Barrier Path | Steps from a threat to the top event. | Red arrow |
| Consequence path | Consequence Path, Mitigative Path, Mitigation Path, Mitigative, Recovery Path, Top Event to Mitigation, Top Event to Consequence, Mitigative Barrier Path | Steps from the top event to a consequence. | Green arrow |
| Escalates | Escalates, Degrades, Escalates Barrier, Degrades Barrier, Escalation, Escalation Factor | An escalation factor's connection to the barrier it weakens. | Amber dashed arrow |
| Controlled by | Controlled By, Controls, Controls Escalation, Escalation Control, Escalation Factor Control | An escalation control's connection to its factor. | Grey dashed arrow |
Leads to, Threat path and Consequence path build the same structure, because the side of a step comes from where it sits. They change only the connector colour. Escalates and Controlled by can be written in either direction.
Where a cell is blank or says Leads to, a connection between an escalation factor and a barrier is read as Escalates, and one between an escalation factor and its control as Controlled by.
What each row leads to
In an edge list, the Connected Node ID on each row is:
| Row | Connected Node ID |
|---|---|
| Hazard | The top event. |
| Threat | Its first preventive barrier, or the top event. |
| Preventive barrier | The next preventive barrier, or the top event. |
| Top event | The first recovery barrier of a path, or a consequence. One row per path. |
| Mitigative barrier | The next mitigative barrier, or the consequence. |
| Consequence | Blank. |
| Escalation factor | The barrier it weakens. |
| Escalation-factor control | Its escalation factor. |