Tags.
RFID and barcode tags carry the GS1 identifiers an event observes. The tag is where the identifier originates; the event is what the gateway validates, stamps and hashes once that identifier reaches the door.
POST /capturePOST /translate
Build state, 29 July 2026. The capture gateway is written and passing its conformance tests; nothing is hosted yet. See How for the dimension, and What ships today for the dated ledger.