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Device

Entity Description​

The Device entity represents a physical hardware unit (IoT device) such as a sensor, actuator, or meter. It is the source of raw data in the system.

JSON Structure​

A typical Device entity in NGSI-LD format looks like this:

{
  "id": "urn:ngsi-ld:Device:Sensor-001",
  "type": "Device",
  "category": {
    "type": "Property",
    "value": ["sensor"]
  },
  "controlledProperty": {
    "type": "Property",
    "value": ["airPollution", "temperature"]
  },
  "batteryLevel": {
    "type": "Property",
    "value": 0.95
  },
  "ipAddress": {
    "type": "Property",
    "value": ["192.168.1.10"]
  },
  "location": {
    "type": "GeoProperty",
    "value": {
      "type": "Point",
      "coordinates": [-3.70379, 40.416775]
    }
  },
  "deviceState": {
    "type": "Property",
    "value": "ok"
  }
}

Key Fields​

  • id: Unique identifier for the device.
  • type: Entity type, must be Device.
  • category: The category of the device (e.g., sensor, actuator, meter).
  • controlledProperty: List of properties the device monitors or controls (e.g., airPollution, trafficFlow).
  • batteryLevel: Current battery level (0.0 to 1.0).
  • deviceState: Operational state of the device (e.g., ok, error).
  • ipAddress: Network address of the device.

Smart Data Models​

This data model follows the Smart Data Models standard for Devices. It aligns with the SAREF (Smart Appliances REFerence) ontology.

Application​

Data Validation​

The openAPI/smartmodels.yaml ensures:

  • Categories: category values must match the allowed enum list (e.g., sensor, actuator).
  • Properties: controlledProperty must be valid strings from the standard list.

Documentation​

  • IoT Integration: Helps IoT engineers understand how to register new devices into the system.
  • Maintenance: Operations teams can use fields like batteryLevel and deviceState to monitor fleet health.

Uniqueness & Linked Data​

  • Uniqueness: batteryLevel is defined as fiware:batteryLevel, ensuring consistent interpretation across different device manufacturers.
  • Linked Data: Devices are linked to the observations they generate (via refDevice in AirQualityObserved) and potentially to the assets they control (via controlledAsset).

Intelligent Query Support​

  • Maintenance Queries: "Find all devices with batteryLevel below 0.2."
  • Capability Queries: "List all devices capable of measuring airPollution in the 'Downtown' district."