HERE Tracking Developer's Guide

Shadows

Shadows provide an effective way to manage configurations for devices that are only intermittently online.

Shadows are stored in HERE Tracking and contain two states of a device's configuration: The reported state and the desired state.

The reported state contains the telemetry that was sent by the device when it was last online.

The desired state contains the settings that will be sent to the device when it next comes online.

IMPORTANT Devices should not communicate directly with this service but should instead send telemetry to the ingestion endpoint only.

Ideally, applications should only write to the desired configuration state and only read from reported configuration state.

Example

A connected heater reports that the temperature of the room in which it is installed is 25°C. This value is stored in the device's reported state.

Reported state
{
  "reported": {
  "payload": {
    "temperature": 25.2
  }
  }
}

The facility management system wants the room temperature lowered and sets the desired value:

Reported state
{
  "desired": {
  "payload": {
    "temperature": 21
  }
  }
}

The next time the device comes online, it will receive this desired state.

The device will then change the temperature of the room and update its shadow again

Reported state
{
  "reported": {
  "payload": {
    "temperature": 21
  }
  }
}