loopback/test/fixtures/simple-integration-app/common/models/appointment.json

{
  "name": "appointment",
  "properties": {
    "date": "date"
  },
  "options": {
    "relations": {
      "physician": {
        "model": "physician",
        "type": "belongsTo",
        "foreignKey": "physicianId"
      },
      "patient": {
        "model": "patient",
        "type": "belongsTo",
        "foreignKey": "patientId"
      }
    }
  }
}