{
  "type": "object",
  "$schema": "http://json-schema.org/draft-04/schema#",
  "id": "https://signalk.org/specification/1.5.1/schemas/definitions.json#",
  "title": "definitions",
  "description": "Reusable definitions of core object types",
  "definitions": {
    "timestamp": {
      "type": "string",
      "description": "RFC 3339 (UTC only without local offset) string representing date and time.",
      "units": "RFC 3339 (UTC)",
      "example": "2014-04-10T08:33:53Z",
      "format": "date-time",
      "pattern" : ".*Z$"
    },
    "source": {
      "type": "object",
      "description": "Source of data in delta format, a record of where the data was received from. An object containing at least the properties defined in 'properties', but can contain anything beyond that.",
      "required": [
        "label"
      ],
      "properties": {
        "label": {
          "type": "string",
          "description": "A label to identify the source bus, eg serial-COM1, eth-local,etc . Can be anything but should follow a predicatable format",
          "example": "N2K-1"
        },
        "type": {
          "type": "string",
          "description": "A human name to identify the type. NMEA0183, NMEA2000, signalk",
          "default": "NMEA2000",
          "example": "NMEA2000"
        },
        "src": {
          "type": "string",
          "description": "NMEA2000 src value or any similar value for encapsulating the original source of the data",
          "example": "36"
        },
        "canName": {
          "type": "string",
          "description": "NMEA2000 can name of the source device",
          "example": "13877444229283709432"
        },
        "pgn": {
          "type": "number",
          "description": "NMEA2000 pgn of the source message",
          "example": "130312"
        },
        "instance": {
          "type": "string",
          "description": "NMEA2000 instance value of the source message"
        },
        "sentence": {
          "type": "string",
          "description": "Sentence type of the source NMEA0183 sentence, $GP[RMC],092750.000,A,5321.6802,N,00630.3372,W,0.02,31.66,280511,,,A*43",
          "example": "RMC"
        },
        "talker": {
          "type": "string",
          "description": "Talker id of the source NMEA0183 sentence, $[GP]RMC,092750.000,A,5321.6802,N,00630.3372,W,0.02,31.66,280511,,,A*43",
          "example": "GP"
        },
        "aisType": {
          "type": "number",
          "multipleOf" : 1,
          "minimum": 1,
          "maximum": 27,
          "description": "AIS Message Type",
          "example":"15"
        }
      }
    },

    "sourceRef": {
      "type": "string",
      "pattern": "^[A-Za-z0-9-_.]*$",
      "description": "Reference to the source under /sources. A dot spearated path to the data. eg [type].[bus].[device]",
      "example": "NMEA0183.COM1.GP"
    },

    "version": {
      "type": "string",
      "description": "Version of the Signal K schema/APIs used by the root object.",
      "pattern": "^[0-9]{1,3}[.][0-9]{1,2}[.][0-9]{1,2}($|-[a-zA-Z0-9]+$)",
      "example": "1.5.0"
    },
    "units": {
      "type": "string",
      "description": "Allowed units of physical quantities. Units should be (derived) SI units where possible.",
      "properties": {
        "s": {
          "display": "s",
          "quantity": "Time",
          "quantityDisplay": "t",
          "description": "Elapsed time (interval) in seconds"
        },
        "Hz": {
          "display": "Hz",
          "quantity": "Frequency",
          "quantityDisplay": "f",
          "description": "Frequency in Hertz"
        },
        "m3": {
          "display": "m\u00b3",
          "quantity": "Volume",
          "quantityDisplay": "V",
          "description": "Volume in cubic meters"
        },
        "m3/s": {
          "display": "m\u00b3/s",
          "quantity": "Flow",
          "quantityDisplay": "Q",
          "description": "Liquid or gas flow in cubic meters per second"
        },
        "kg/s": {
          "display": "kg/s",
          "quantity": "Mass flow rate",
          "quantityDisplay": "\u1e41",
          "description": "Liquid or gas flow in kilograms per second"
        },
        "kg/m3": {
          "display": "kg/m\u00b3",
          "quantity": "Density",
          "quantityDisplay": "\u03c1",
          "description": "Density in kg per cubic meter"
        },
        "deg": {
          "display": "\u00b0",
          "quantity": "Angle",
          "quantityDisplay": "\u2220",
          "description": "Latitude or longitude in decimal degrees"
        },
        "rad": {
          "display": "\u33ad",
          "quantity": "Angle",
          "quantityDisplay": "\u2220",
          "description": "Angular arc in radians"
        },
        "rad/s": {
          "display": "\u33ad/s",
          "quantity": "Rotation",
          "quantityDisplay": "\u03c9",
          "description": "Angular rate in radians per second"
        },
        "A": {
          "display": "A",
          "quantity": "Current",
          "quantityDisplay": "I",
          "description": "Electrical current in ampere"
        },
        "C": {
          "display": "C",
          "quantity": "Charge",
          "quantityDisplay": "Q",
          "description": "Electrical charge in Coulomb"
        },
        "V": {
          "display": "V",
          "quantity": "Voltage",
          "quantityDisplay": "V",
          "description": "Electrical potential in volt"
        },
        "W": {
          "display": "W",
          "quantity": "Power",
          "quantityDisplay": "P",
          "description": "Power in watt"
        },
        "Nm": {
          "display": "Nm",
          "quantity": "Torque",
          "quantityDisplay": "\u03c4",
          "description": "Torque in Newton meter"
        },
        "J": {
          "display": "J",
          "quantity": "Energy",
          "quantityDisplay": "E",
          "description": "Electrical energy in joule"
        },
        "ohm": {
          "display": "\u2126",
          "quantity": "Resistance",
          "quantityDisplay": "R",
          "description": "Electrical resistance in ohm"
        },
        "m": {
          "display": "m",
          "quantity": "Distance",
          "quantityDisplay": "d",
          "description": "Distance in meters"
        },
        "m/s": {
          "display": "m/s",
          "quantity": "Speed",
          "quantityDisplay": "v",
          "description": "Speed in meters per second"
        },
        "m2": {
          "display": "\u33a1",
          "quantity": "Area",
          "quantityDisplay": "A",
          "description": "(Surface) area in square meters"
        },
        "K": {
          "display": "K",
          "quantity": "Temperature",
          "quantityDisplay": "T",
          "description": "Temperature in kelvin"
        },
        "Pa": {
          "display": "Pa",
          "quantity": "Pressure",
          "quantityDisplay": "P",
          "description": "Pressure in pascal"
        },
        "kg": {
          "display": "kg",
          "quantity": "Mass",
          "quantityDisplay": "m",
          "description": "Mass in kilogram"
        },
        "ratio": {
          "display": "",
          "quantity": "Ratio",
          "quantityDisplay": "\u03c6",
          "description": "Relative value compared to reference or normal value. 0 = 0%, 1 = 100%, 1e-3 = 1 ppt"
        },
        "m/s2": {
          "display": "m/s\u00b2",
          "quantity": "Acceleration",
          "quantityDisplay": "a",
          "description": "Acceleration in meters per second squared"
        },
        "rad/s2": {
          "display": "rad/s\u00b2",
          "quantity": "Angular acceleration",
          "quantityDisplay": "a",
          "description": "Angular acceleration in radians per second squared"
        },
        "N": {
          "display": "N",
          "quantity": "Force",
          "quantityDisplay": "F",
          "description": "Force in newton"
        },
        "T": {
          "display": "T",
          "quantity": "Magnetic field",
          "quantityDisplay": "B",
          "description": "Magnetic field strength in tesla"
        },
        "Lux": {
          "display": "lx",
          "quantity": "Light Intensity",
          "quantityDisplay": "Ev",
          "description": "Light Intensity in lux"
        },
        "Pa/s": {
          "display": "Pa/s",
          "quantity": "Pressure rate",
          "quantityDisplay": "R",
          "description": "Pressure change rate in pascal per second"
        },
        "Pa.s": {
          "display": "Pa s",
          "quantity": "Viscosity",
          "quantityDisplay": "\u03bc",
          "description": "Viscosity in pascal seconds"
        }
      }
    },
    "mmsi": {
      "type": "string",
      "description": "Maritime Mobile Service Identity (MMSI). Has to be 9 digits. See http://en.wikipedia.org/wiki/Maritime_Mobile_Service_Identity for information.",
      "pattern": "^[2-7][0-9]{8}$",
      "example": "503123456"
    },
    "aircraftMmsi": {
      "type": "string",
      "description": "Maritime Mobile Service Identity (MMSI) for aircraft. Has to be 9 digits. See http://en.wikipedia.org/wiki/Maritime_Mobile_Service_Identity for information.",
      "pattern": "^1[0-9]{8}$",
      "example": "103123456"
    },
    "atonMmsi": {
      "type": "string",
      "description": "Maritime Mobile Service Identity (MMSI) for . Has to be 9 digits. See http://en.wikipedia.org/wiki/Maritime_Mobile_Service_Identity for information.",
      "pattern": "^99[0-9]{7}$",
      "example": "993123456"
    },
    "sarMmsi": {
      "type": "string",
      "description": "Maritime Mobile Service Identity (MMSI) for . Has to be 9 digits. See http://en.wikipedia.org/wiki/Maritime_Mobile_Service_Identity for information.",
      "pattern": "^97[0-9]{7}$",
      "example": "973123456"
    },
    "uuid": {
      "type": "string",
      "description": "A unique Signal K flavoured maritime resource identifier (MRN). A MRN is a form of URN, following a specific format: urn:mrn:<issueing authority>:<id type>:<id>. In case of a Signal K uuid, that looks like this: urn:mrn:signalk:uuid:<uuid>, where Signal K is the issuing authority and UUID (v4) the ID type.",
      "pattern": "^urn:mrn:signalk:uuid:[0-9A-Fa-f]{8}-[0-9A-Fa-f]{4}-4[0-9A-Fa-f]{3}-[89ABab][0-9A-Fa-f]{3}-[0-9A-Fa-f]{12}$",
      "example": "urn:mrn:signalk:uuid:b7590868-1d62-47d9-989c-32321b349fb9"
    },
    "url": {
      "type": "string",
      "description": "A location of a resource, potentially relative. For hierarchical schemes (like http), applications must resolve relative URIs (e.g. './v1/api/'). Implementations should support the following schemes: http:, https:, mailto:, tel:, and ws:.",
      "example": "http://localhost:8080/signalk/v1/api/vessels/self/environment"
    },

    "commonValueFields": {
      "type": "object",
      "required": ["timestamp", "$source"],
      "properties": {
        "timestamp": {
          "$ref": "#/definitions/timestamp"
        },

        "$source": {
          "$ref": "#/definitions/sourceRef"
        },

        "_attr": {
          "$ref": "#/definitions/_attr"
        },

        "meta": {
          "$ref": "#/definitions/meta"
        },
        "pgn": {
          "type": "number"
        },
        "sentence": {
          "type": "string"
        }
      }
    },

    "numberValue": {
      "type": "object",
      "description": "Data should be of type number.",
      "allOf": [{
        "$ref": "#/definitions/commonValueFields"
      }, {
        "properties": {
          "value": {
            "type": "number"
          },
          "values": {
            "type": "object",
            "patternProperties": {
              ".*": {
                "$ref": "#/definitions/valuesNumberValue"
              }
            }
          }
        }
      }]
    },

    "valuesNumberValue": {
      "type": "object",
      "properties": {
        "value": {
          "type": "number"
        },
        "timestamp": {
          "$ref": "#/definitions/timestamp"
        },
        "pgn": {
          "type": "number"
        },
        "sentence": {
          "type": "string"
        }
      }
    },

    "stringValue": {
      "type": "object",
      "description": "Data should be of type number.",
      "allOf": [{
        "$ref": "#/definitions/commonValueFields"
      }, {
        "properties": {
          "value": {
            "type": "string"
          },
          "values": {
            "type": "object",
            "patternProperties": {
              ".*": {
                "$ref": "#/definitions/valuesStringValue"
              }
            }
          }
        }
      }]
    },

    "valuesStringValue": {
      "type": "object",
      "properties": {
        "value": {
          "type": "string"
        },
        "timestamp": {
          "$ref": "#/definitions/timestamp"
        },
        "pgn": {
          "type": "number"
        },
        "sentence": {
          "type": "string"
        }
      }
    },


    "datetimeValue": {
      "type": "object",
      "description": "Data should be of type number.",
      "allOf": [{
        "$ref": "#/definitions/commonValueFields"
      }, {
        "properties": {
          "value": {
            "type": "string",
            "format": "date-time"
          },
          "values": {
            "type": "object",
            "patternProperties": {
              ".*": {
                "$ref": "#/definitions/valuesDatetimeValue"
              }
            }
          }
        }
      }]
    },

    "valuesDatetimeValue": {
      "type": "object",
      "properties": {
        "value": {
          "type": "string",
          "format": "date-time"
        },
        "timestamp": {
          "$ref": "#/definitions/timestamp"
        },
        "pgn": {
          "type": "number"
        },
        "sentence": {
          "type": "string"
        }
      }
    },


    "nullValue": {
      "type": "object",
      "description": "Data should be of type NULL.",
      "properties": {
        "value": {
          "type": "null"
        },

        "timestamp": {
          "$ref": "#/definitions/timestamp"
        },

        "source": {
          "$ref": "#/definitions/source"
        },

        "_attr": {
          "$ref": "#/definitions/_attr"
        },

        "meta": {
          "$ref": "#/definitions/meta"
        }
      }
    },

    "_attr": {
      "type": "object",
      "title": "_attr schema.",
      "description": "Filesystem specific data, e.g. security, possibly more later.",
      "properties": {
        "_mode": {
          "type": "integer",
          "title": "_mode schema.",
          "description": "Unix style permissions, often written in `owner:group:other` form, `-rw-r--r--`",
          "default": 644
        },
        "_owner": {
          "type": "string",
          "title": "_owner schema.",
          "description": "The owner of this resource.",
          "default": "self"
        },
        "_group": {
          "type": "string",
          "title": "_group schema.",
          "description": "The group owning this resource.",
          "default": "self"
        }
      }
    },

    "alarmState": {
      "type": "string",
      "title": "alarmState",
      "description": "The alarm state when the value is in this zone.",
      "default": "normal",
      "enum": [
        "nominal",
        "normal",
        "alert",
        "warn",
        "alarm",
        "emergency"
      ]
    },
    "alarmMethodEnum": {
      "enum": [
        "visual",
        "sound"
      ]
    },

    "meta": {
      "type": "object",
      "title": "Meta schema.",
      "description": "Provides meta data to enable alarm and display configuration.",
      "required": ["description"],
      "properties": {
        "displayName": {
          "type": "string",
          "title": "DisplayName schema.",
          "description": "A display name for this value. This is shown on the gauge and should not include units.",
          "example": "Tachometer, Engine 1"
        },

        "longName": {
          "type": "string",
          "title": "LongName schema.",
          "description": "A long name for this value.",
          "example": "Tachometer, Engine 1"
        },

        "shortName": {
          "type": "string",
          "title": "ShortName schema.",
          "description": "A short name for this value.",
          "example": "Tacho 1"
        },

        "description": {
          "type": "string",
          "title": "Description schema.",
          "description": "Description of the SK path.",
          "example": "Engine revolutions (x60 for RPM)"
        },

        "enum": {
          "type": "array",
          "title": "Permissible values",
          "description": "List of permissible values",
          "example": ["stopped", "started", "unusable"]
        },

        "properties": {
          "type": "object",
          "title": "Properties for object valued properties",
          "patternProperties": {
            ".*": {
              "type": "object",
              "properties": {
                "type": {
                  "type": "string"
                },
                "title": {
                  "type": "string"
                },
                "description": {
                  "type": "string"
                },
                "units": {
                  "type": "string"
                },
                "example": {
                  "type": [
                    "string",
                    "number",
                    "boolean",
                    "object"
                  ]
                }
              }
            }
          }
        },

        "gaugeType": {
          "type": "string",
          "title": "gaugeType schema.",
          "description": "gaugeType is deprecated. The type of gauge necessary to display this value.",
          "example": "sparkline"
        },

        "displayScale": {
          "type": "object",
          "title": "Scale to display.",
          "description": "Gives details of the display scale against which the value should be displayed",
          "properties": {
            "lower": {
              "type": "number",
              "title": "Display lower limit.",
              "description": "The suggested lower limit for the pointer (or equivalent) on the display",
              "example": 0
            },
            "upper": {
              "type": "number",
              "title": "Display upper limit.",
              "description": "The suggested upper limit for the pointer (or equivalent) on the display",
              "example": 4000
            },
            "type": {
              "type": "string",
              "enum": [
                "linear",
                "logarithmic",
                "squareroot",
                "power"
              ],
              "title": "Scale type used on the display.",
              "description": "The suggested type of scale to use",
              "example": "logarithmic"
            },
            "power": {
              "type": "number",
              "title": "Selected power for display scale",
              "description": "The power to use when the displayScale/type is set to 'power'. Can be any numeric value except zero.",
              "example": 2
            }
          },
          "oneOf": [
            {
              "required": [
                "lower",
                "upper"
              ],
              "properties": {
                "lower": {},
                "upper": {}
              },
              "additionalProperties": false
            },
            {
              "required": [
                "lower",
                "upper",
                "type"
              ],
              "properties": {
                "lower": {},
                "upper": {},
                "type": {
                  "enum": [
                    "linear",
                    "squareroot",
                    "logarithmic"
                  ]
                }
              },
              "additionalProperties": false
            },
            {
              "required": [
                "lower",
                "upper",
                "type",
                "power"
              ],
              "properties": {
                "lower": {},
                "upper": {},
                "type": {
                  "enum": [
                    "power"
                  ]
                },
                "power": {}
              },
              "additionalProperties": false
            }
          ]
        },
        "units": {
          "type": "string",
          "title": "units schema.",
          "description": "The (derived) SI unit of this value.",
          "example": "m/s"
        },
        "timeout": {
          "type": "number",
          "title": "Timeout",
          "description": "The timeout in (fractional) seconds after which this data is invalid.",
          "example": 2
        },

        "alertMethod": {
          "type": "array",
          "title": "Alert Method",
          "description": "The method to use to raise the alert. An alert is an event that should be known",
          "default": ["visual"],
          "items": {
            "$ref": "#/definitions/alarmMethodEnum"
          }
        },
        "warnMethod": {
          "type": "array",
          "title": "Warn Method",
          "description": "The method to use to raise the warning. A warning is an unexpected event that may require attention",
          "default": ["visual"],
          "items": {
            "$ref": "#/definitions/alarmMethodEnum"
          }
        },

        "alarmMethod": {
          "type": "array",
          "title": "Alarm Method",
          "description": "The method to use to raise the alarm. An alarm requires immediate attention, eg no oil pressure",
          "default": ["visual", "sound"],
          "items": {
            "$ref": "#/definitions/alarmMethodEnum"
          }
        },
        "emergencyMethod": {
          "type": "array",
          "title": "Emergency Method",
          "description": "The method to use to raise an emergency. An emergency is an immediate danger to life or vessel",
          "default": ["visual", "sound"],
          "items": {
            "$ref": "#/definitions/alarmMethodEnum"
          }
        },

        "zones": {
          "type": "array",
          "title": "Zones schema.",
          "description": "The zones defining the range of values for this signalk value.",
          "items": {
            "type": "object",
            "title": "zone",
            "description": "A zone used to define the display and alarm state when the value is in between bottom and top.",
            "required": ["state"],
            "properties": {
              "lower": {
                "id": "lower",
                "type": "number",
                "title": "Lower",
                "description": "The lowest number in this zone",
                "name": "lower",
                "example": 3500
              },

              "upper": {
                "id": "upper",
                "type": "number",
                "title": "Upper",
                "description": "The highest value in this zone",
                "name": "upper",
                "example": 4000
              },

              "state": {
                "$ref": "#/definitions/alarmState"
              },

              "message": {
                "id": "message",
                "type": "string",
                "title": "message",
                "description": "The message to display for the alarm.",
                "default": "Warning"
              }
            }
          }
        }
      }
    },
    "geohash": {
      "type": "string",
      "description": "A geohash (see http://geohash.org)",
      "pattern": "^[0-9A-Za-z:]{1,}$",
      "example": "eg rbe:TasmanBay"
    },
    "position": {
      "type": "object",
      "title": "position",
      "description": "The position in 3 dimensions",
      "allOf": [
        {
          "$ref": "#/definitions/commonValueFields"
        },
        {
          "properties": {
            "value": {
              "type": "object",
              "required": [
                "latitude",
                "longitude"
              ],
              "properties": {
                "longitude": {
                  "type": "number",
                  "description": "Longitude",
                  "units": "deg",
                  "example": 4.98765245
                },
                "latitude": {
                  "type": "number",
                  "description": "Latitude",
                  "units": "deg",
                  "example": 52.0987654
                },
                "altitude": {
                  "type": "number",
                  "description": "Altitude",
                  "units": "m"
                }
              }
            },
            "values": {
              "type": "object",
              "patternProperties": {
                ".*": {
                  "type": "object",
                  "properties": {
                    "timestamp": {
                      "$ref": "#/definitions/timestamp"
                    },
                    "pgn": {
                      "type": "number"
                    },
                    "sentence": {
                      "type": "string"
                    },
                    "value": {
                      "type": "object",
                      "properties": {
                        "longitude": {
                          "type": "number",
                          "description": "Longitude",
                          "units": "deg",
                          "example": 4.98765245
                        },
                        "latitude": {
                          "type": "number",
                          "description": "Latitude",
                          "units": "deg",
                          "example": 52.0987654
                        },
                        "altitude": {
                          "type": "number",
                          "description": "Altitude",
                          "units": "m"
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      ]
    },
    "waypoint": {
      "type": "object",
      "description": "A waypoint, an object with a signal k position object, and GeoJSON Feature object (see geojson.org, and https://github.com/fge/sample-json-schemas/tree/master/geojson)",
      "properties": {
        "position": {
          "$ref": "#/definitions/position"
        },
        "feature": {
          "title": "Feature",
          "description": "A Geo JSON feature object",
          "required": [
            "geometry",
            "properties"
          ],
          "properties": {
            "type": {
              "enum": [
                "Feature"
              ]
            },
            "geometry": {
              "title": "Point",
              "properties": {
                "type": {
                  "enum": [
                    "Point"
                  ]
                },
                "coordinates": {
                  "description": "A single position, in x,y order (Lon, Lat)",
                  "type": "array",
                  "minItems": 2,
                  "items": [{
                    "type": "number"
                  }, {
                    "type": "number"
                  }],
                  "additionalItems": false
                }
              }
            },
            "properties": {
              "type": [
                "object",
                "null"
              ],
              "description": "Additional data of any type",
              "additionalProperties": true
            },
            "id": {
              "FIXME": "may be there, type not known (string? number?)"
            }
          }
        }
      }
    }
  }
}