Impact analysis and deprecation

How do you find what breaks and who still uses an asset, when lineage alone cannot say?

Lineage has no value as a graph. It has value as an answer to two questions:

1. What breaks if I change this? This needs downstream traversal plus ranking, because unranked traversal returns the whole warehouse.
2. Who still uses this? Lineage cannot answer this. Lineage describes declared structure; usage is behaviour. This question belongs to telemetry (usage logs).

Failing to separate these two is why deprecation programs stall: teams query the dependency graph, find 3,000 edges, and give up.

The workable pattern is a pipeline:

1. Lineage narrows the candidate set structurally (3,000 assets reduced to those that truly consume the table).
2. Telemetry ranks the candidates by actual reads (who read it recently, how often).
3. A mandatory denial channel confirms the long tail (revoke access, log who is refused).

Each stage is unreliable alone. The combination is sound.