Knobit of Data modelling · K-704 · Skill

Recognises a derived or copied column without a check

What it means

A column carrying `derivation` — a stored total, a copied name, a path string — with no check comparing it with a fresh computation. The update anomaly was accepted on purpose; the check is what makes it safe. A snapshot meant to keep the value as it was is not a copy and needs no check: say so in the `derivation`.

How it is assessed

Flags the deficient case and passes the acceptable one. Deficient: `account.holder_name` copied from `party.name` with `derivation: "copied by ETL"`; the ETL step is disabled in a refactor and nobody notices for a year Acceptable: `DQ-021`, `dimension: consistency`, `scope: set`, comparing `account.holder_name` with `party.name` through `holder_party_id`, `backs: [PE-057]` (`DQR-019`)

Builds on

Recognises a stored derived or summary valueK-603 · Skill
Recognises an unmanaged duplicate columnK-601 · Skill
Explains derived data and point-in-time snapshotsK-565 · Knowledge

Needed by

None