Evidence That Can Be Traced
Traceability isn't a source column; it's every number reaching back to its raw fact.
People say a system is “traceable” when it stores a source_url next to each record. That’s a citation, not a trail. A real trail means any derived number can be walked backward through every step that produced it, down to the raw fact — and that the intermediate facts are still there to walk through.
The mechanism I keep returning to is append-only evidence. Facts, extracted chunks, calculations, and sources each live in their own store, and nothing is ever overwritten; a correction is a new fact that supersedes an old one, not a mutation that erases it. A number in a report then isn’t a value — it’s a handle you can follow.
Seed note. The open question is granularity: trace every arithmetic operation, or every meaningful fact? Too fine and the trail is noise; too coarse and it can’t answer “why this number.” I don’t have the line yet.