The purchase order a tracing document belongs to, with the sales orders that replacing or deleting the document would also affect: those linked to the purchase order, then its own sales order last. A document attached through links resolves to the purchase order supplied from those links' origin node. 404 when the document, the purchase order or its own sales order is missing or removed; 422 (document_is_origin_order) when the document hangs off an origin-country link. Not scoped to the caller's company.