Lineage
Lineage is each number's path from its source through every table to the dashboard.
The transformation layer records lineage as it builds the data model, in the same step that filters out test orders, removes duplicates, and joins tables. With it, a number on a dashboard can be traced through every table to the source system that recorded it: an ad platform, the store, or site analytics.
Lineage is part of the test for AI-ready data: the tables under each metric pass their data tests, with lineage back to the source system. A data test finds rows breaking a rule; lineage traces those rows to their table and source, so the fix goes to that table.
Example
If return on ad spend (ROAS) doubles overnight, the analyst looks for a duplicated order, a missing refund, or a campaign credited to the wrong channel before the numbers go out. Lineage traces each part of that ROAS to its source: spend to each ad platform, orders and refunds to the store.