{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "CityJSON Extension specifications v2.0",
  "type": "object",

  "definitions": {

    "Plus": {
      "patternProperties": {
        "(\\+)\\w+": {}
      },
      "additionalProperties": false
    }

  },


  "properties": {
    "type": { "enum": ["CityJSONExtension"] },
    "name": { 
      "type": "string",
      "pattern": "^\\w[a-zA-Z@#0-9._]*$",
      "description": "no spaces allowed"
    },

    "version": { 
      "type": "string",
      "pattern": "^(\\d\\.)(\\d+\\.)?(\\*|\\d+)$"
    },

    "versionCityJSON": { 
      "type": "string",
      "pattern": "^(\\d\\.)(\\d)$"
    },

    "url": {
      "type": "string",
      "format": "uri-reference",
      "description": "good to host the extension at a URL so that others can access it"
    },

    "description": { "type": "string" },
    
    "extraRootProperties":{
      "patternProperties": {
        "(\\+|\\@)\\w+": {}
      },
      "additionalProperties": false
    },

    "extraAttributes": {
      "type": "object",
      "properties": {
        "Bridge": { "$ref": "#/definitions/Plus" },
        "BridgeConstructiveElement": { "$ref": "#/definitions/Plus" },
        "BridgeFurniture": { "$ref": "#/definitions/Plus" },
        "BridgeInstallation": { "$ref": "#/definitions/Plus" },
        "BridgePart": { "$ref": "#/definitions/Plus" },
        "BridgeRoom": { "$ref": "#/definitions/Plus" },
        "Building": { "$ref": "#/definitions/Plus" },
        "BuildingPart": { "$ref": "#/definitions/Plus" },
        "BuildingConstructiveElement": { "$ref": "#/definitions/Plus" },
        "BuildingFurniture": { "$ref": "#/definitions/Plus" },
        "BuildingInstallation": { "$ref": "#/definitions/Plus" },
        "BuildingRoom": { "$ref": "#/definitions/Plus" },
        "BuildingStorey": { "$ref": "#/definitions/Plus" },
        "BuildingUnit": { "$ref": "#/definitions/Plus" },
        "CityFurniture": { "$ref": "#/definitions/Plus" },
        "CityObjectGroup": { "$ref": "#/definitions/Plus" },
        "GenericCityObject": { "$ref": "#/definitions/Plus" },
        "LandUse": { "$ref": "#/definitions/Plus" },
        "OtherConstruction": { "$ref": "#/definitions/Plus" },
        "PlantCover": { "$ref": "#/definitions/Plus" },
        "Railway": { "$ref": "#/definitions/Plus" },
        "Road": { "$ref": "#/definitions/Plus" },
        "SolitaryVegetationObject": { "$ref": "#/definitions/Plus" },
        "TINRelief": { "$ref": "#/definitions/Plus" },
        "TransportSquare": { "$ref": "#/definitions/Plus" },
        "Tunnel": { "$ref": "#/definitions/Plus" },
        "TunnelConstructiveElement": { "$ref": "#/definitions/Plus" },
        "TunnelFurniture": { "$ref": "#/definitions/Plus" },
        "TunnelHollowSpace": { "$ref": "#/definitions/Plus" },
        "TunnelInstallation": { "$ref": "#/definitions/Plus" },
        "TunnelPart": { "$ref": "#/definitions/Plus" },
        "WaterBody": { "$ref": "#/definitions/Plus" },
        "Waterway": { "$ref": "#/definitions/Plus" }
      },
      "additionalProperties": false
    },

    "extraCityObjects": {
      "patternProperties": {
        "(\\+)([A-Z])\\w+": {}
      },
      "additionalProperties": false
    },

    "extraSemanticSurfaces": {
      "patternProperties": {
        "(\\+)([A-Z])\\w+": {}
      },
      "additionalProperties": false
    }

  },
  "anyOf": [
    {
      "required": [
        "url"
      ]
    },
    {
      "required": [
        "uri"
      ]
    }
  ], 
  "required": ["type", "name", "version", "versionCityJSON", "extraAttributes", "extraCityObjects", "extraRootProperties", "extraSemanticSurfaces"]
}