Parents and children
Every production run consumes input lots and produces output lots. Genealogy is the link between them: the output is the child, the inputs are its parents, and following those links in either direction is what traceability actually consists of.
A useful genealogy record holds more than the fact of a link. It holds quantity, so you know how much of a parent went into a child, and it holds time, so the sequence can be reconstructed later.
Backward tracing answers "what is in this?"
Start from a finished lot - usually because of a complaint, a test result, or a customer question - and walk up through its parents to the raw materials and suppliers behind it.
This is how you find a root cause, and how you discover which other products share the same suspect input. It is also what a customer means when they ask you to substantiate a claim about a specific delivery.
Forward tracing answers "where did this go?"
Start from a raw material lot - usually because a supplier has issued a notice - and walk down through every batch it entered and every shipment those batches fed.
This is how you scope a withdrawal. The precision of the answer decides how much product you pull: vague records force you to withdraw everything from a period, while precise ones let you withdraw what is actually affected and defend the boundary.
The events that break the chain
Genealogy rarely fails at the obvious steps. It fails at the ones that feel administrative on the floor.
- Blending - several parents produce one child, and recording only the largest input loses the rest
- Splitting - one parent becomes several children, each of which must keep the link
- Rework - an output becomes an input again, creating a loop that naive records cannot represent
- Partial consumption - a container is opened, some is used, and the remainder returns to stock still carrying its identity
- Repacking - material moves into different containers and quietly acquires a new internal reference nobody can map back
Why quantity matters as much as linkage
Knowing that lot A contributed to lot B is useful. Knowing how much of A went into B is what lets you reconcile, and reconciliation is what exposes a missing record.
If a parent lot of 1,000 kg shows 600 kg consumed across its children and 200 kg still in stock, the missing 200 kg is a question worth asking. Without quantities on the links, that discrepancy is invisible and the gap stays hidden until an audit finds it.
One-up, one-back is the interoperable unit
No single business sees a whole supply chain. What each party can hold reliably is the step above and the step below: who supplied this lot, and who received it.
If every party in a chain holds that accurately and shares a consistent lot code, the full chain can be reconstructed by walking from one party to the next - which is precisely the design regulators rely on.