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Generate fault trees, bow-ties, event trees, reliability block diagrams, GSN arguments and Markov models from Power BI data with the Ataytis Assurance visual.

Ataytis Assurance · Event Tree Analysis

Event Tree Analysis

What the event tree analysis (ETA) diagram type draws, what it calculates from your numbers, the standards that describe it, and its defaults.

What it draws

Event Tree Analysis draws what can follow an initiating event, such as a release, a power loss or a cyber incident. At each pivotal event, such as a safety system, a backup or an operator action that works or fails, the path splits into a success branch and a failure branch. Every path ends in an outcome, and each path from the initiating event to an outcome is one sequence.

The tree reads left to right, with success above failure at every split.

The Ataytis Assurance advanced editor with an event tree in the preview, branching left to right from an initiating event to its outcomes.
An event tree in the advanced editor preview, with the Diagram tab settings on the right.

What it calculates

Event Tree Analysis is the one diagram type that calculates, because the arithmetic of an event tree has one agreed form. From your branch probabilities and initiating frequency, it works out three things for each sequence and writes them on the sequence's outcome.

CalculatedHow
Sequence identifierThe initiating event's Node ID, then S, F or C and the branch's position at each split, such as IE-S1-F2.
Path probabilityThe branch probabilities along the path, multiplied together.
Sequence frequencyThe initiating frequency multiplied by the path probability, in the same units as the initiating frequency.

It does not calculate uncertainty, importance measures or minimal cut sets, and it does not add sequences up by outcome. Nothing is calculated from values the data does not supply, and a tree with no probabilities still draws.

Standards

The IEC 62502:2010 profile is designed with reference to IEC 62502:2010, Analysis techniques for dependability – Event tree analysis (ETA). Event tree analysis also appears in IEC 31010:2019, IEC 60300-3-1:2003, IEC 61511-3:2016, ISO/TR 24971:2020 and EN 50126-2:2017. Notation standards lists what each one covers.

Defaults

SettingDefault
Notation profileCustom. IEC 62502:2010 is also available.
OrientationLeft to right. Right to left, top to bottom and bottom to top are also available.
Connected node is read asThe node before this row
Required mappingsNode ID, Node type and Relationship type
Node type when the cell is blankPivotal event
Relationship type when the cell is blankSequence
Connector routingOrthogonal
Sequence identifierShow on outcome
Sequence frequencyShow on outcome
Quantity formatScientific
Advisory diagnosticsShow advisories

In this section

Preparing event tree dataOne row per node, which row each branch value goes on, and a complete example.Event tree node and relationship typesWhat to write in Node Type and Relationship Type, and how each is drawn.Sequences and frequenciesHow sequences are numbered and quantified, and the rules the numbers follow.Reading an event treeLayout, notation profiles, the summary strip, the Node Inspector and focus.Event tree validationRules, messages and fixes, and advisories.
Event Tree Analysis — Ataytis Assurance | AtaytisTech