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archlab 1.0 er
title "Parcel delivery"
description "One shipment, exactly one label, at most one signature, and the parcels that make it up."

@er
  entity shipment "Shipment" [PostgreSQL]
    desc "One dispatch to one address. Created when the picking is finished, never before."
    attr id uuid pk
    attr order_id uuid fk
    attr carrier_id uuid fk
    attr dispatched_at timestamp
  entity carrier "Carrier"
    attr id uuid pk
    attr name string uk
    attr tracking_url_template string
  entity parcel "Parcel"
    desc "A physical box. A shipment too heavy for one box becomes several, all travelling together."
    attr id uuid pk
    attr shipment_id uuid fk
    attr weight_g integer
  entity label "Shipping label"
    desc "Printed once per shipment and never reprinted — a second label is a second shipment, because the carrier has already scanned the first."
    attr shipment_id uuid pk fk
    attr tracking_code string uk
    attr printed_at timestamp
  entity signature "Signature"
    desc "Captured on delivery, when the service level asks for one. Most parcels are left in a safe place and have none."
    attr shipment_id uuid pk fk
    attr signed_by string
    attr captured_at timestamp

carrier ||--o{ shipment : carries
  shipment ||--|| label : "is printed as"
  shipment ||--o| signature : "is signed for by"
  parcel }|--|| shipment : "travels in"

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