{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$defs": {
    "SpaceRef": {
      "properties": {
        "root_id": {
          "type": "string",
          "pattern": "^rt_[0-9a-f]{32}$"
        },
        "space_id": {
          "type": "string",
          "pattern": "^spc_[0-9a-f]{32}$"
        }
      },
      "additionalProperties": false,
      "type": "object",
      "required": [
        "root_id",
        "space_id"
      ],
      "description": "SpaceRef is the exact identity of one continuing space and its journal."
    }
  },
  "properties": {
    "space": {
      "$ref": "#/$defs/SpaceRef"
    }
  },
  "additionalProperties": false,
  "type": "object",
  "required": [
    "space"
  ],
  "title": "HeadRequest",
  "description": "HeadRequest selects one space's committed cutoff."
}