The investigation

How the cause was established, and what was found.

The part

What it is

Repeated questioning of why is adequate for most cases and does not require a formal method.

What matters is stopping at a cause that can actually be changed rather than at one that assigns responsibility.

The smallest level

The attributes it carries

Each attribute is one of the framework’s shared types. What a date is, and how it is written, is defined once for the whole model — the note here says what it means in this particular place.

Root cause
What actually produced the defect.
Text shared type
Cause category
Method, machine, material, measurement, environment or people.
Choice shared type
Source
How it was established — evidence rather than inference.
Source shared type