The five-layer controls topology. Instructions move down, status moves up, and your working knowledge is deepest at the bottom two layers.
| The decision | Layer that owns it |
|---|---|
| Release this wave to the floor | WMS, L4 |
| Sequence orders into batches | WES if present, else WMS |
| Divert this carton to lane 5 | WCS decides L3; PLC fires L1 |
| Stop this zone, it's jammed | PLC, local logic, L1 |
| Format the read for the WMS | Middleware, L2 |