{
  "type": "object",
  "properties": {
    "building_groups": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "group_id": {"type": "string", "pattern": "^[a-z0-9][a-z0-9_]*$"},
          "anchor_loc": {"type": "string", "pattern": "^[A-Za-z0-9_]+$"},
          "kind": {"type": "string", "enum": ["chain_bg", "prev_shot_ref"]},
          "rationale": {"type": "string"}
        },
        "required": ["group_id", "anchor_loc", "kind", "rationale"],
        "additionalProperties": false
      }
    }
  },
  "required": ["building_groups"],
  "additionalProperties": false
}