IoT Device Registry Schema

erDiagram
  CUSTOMER ||--o{ SITE : owns
  SITE ||--o{ DEVICE : hosts
  DEVICE_MODEL ||--o{ DEVICE : "type of"
  DEVICE_MODEL ||--o{ FIRMWARE_VERSION : releases
  FIRMWARE_VERSION ||--o{ DEVICE : "running on"
  DEVICE ||--o{ CERTIFICATE : "identified by"
  DEVICE ||--o{ DEVICE_EVENT : logs
  DEVICE {
    string serial PK
    int site_id FK
    int model_id FK
    int firmware_id FK
    string status
  }
  FIRMWARE_VERSION {
    int id PK
    int model_id FK
    string version
    date released_on
  }
  CERTIFICATE {
    string thumbprint PK
    string device_serial FK
    date expires_on
  }
  DEVICE_EVENT {
    int id PK
    string device_serial FK
    string type
    datetime at
  }