{
  "entities": {
    "reservation":   { "key": "res_id", "fields": { "fare": ["basic", "standard", "flex"], "refundable": "bool", "paid": "number", "no_show": "bool" } },
    "passenger":     { "key": "pax_id", "fields": { "tier": ["regular", "silver", "gold"] } },
    "target_flight": { "key": "flight_no", "fields": { "same_day": "bool" }, "nullable": true }
  },
  "relations": { "holds": "passenger -> reservation", "to": "rebook -> target_flight" },
  "acts": {
    "rebook":        { "of": "reservation", "to": "target_flight", "outcomes": ["granted", "granted_with_fee", "refused"] },
    "cancel_refund": { "of": "reservation", "outcomes": ["granted", "refused"] }
  },
  "trace": {
    "acts": ["rebook", "cancel_refund", "none"],
    "outcomes": ["granted", "granted_with_fee", "refused", "null"],
    "fields": { "amount": "number" }
  }
}