{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://rig.works/schemas/rig.book.subject.schema.json",
  "title": "rig.book.subject",
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "work": {
      "$ref": "./_defs.schema.json#/$defs/entity"
    },
    "scheme": {
      "type": "string",
      "enum": [
        "thema",
        "bisac",
        "bic",
        "dewey",
        "keyword"
      ]
    },
    "code": {
      "$ref": "./_defs.schema.json#/$defs/string"
    },
    "heading": {
      "$ref": "./_defs.schema.json#/$defs/string"
    }
  },
  "required": [
    "work"
  ],
  "description": "One classification heading on one work. Field meanings follow ONIX Subject.",
  "minProperties": 2
}