Live Objects - complete developer guide

Data Message

When a LWM2M device reports value changes, a data message that includes this change is generated by LiveObjects under certain conditions:

the report must be at the device initiative (send, or notify but not read response),
the report must match a given data rule of the tenant.

When all these conditions are met, a message is generated.

Today the generation model used for the message is twin_json.

DataMessage common attributes

A Twin data message as other LiveObjects messages, will embed some common attributes: id, streamId, etc.

The value part of the message will embed the device reported values representation, depending on the model used.

Example of a fill Twin data message having twin_json model:

{
  "id": "6254192e1a52727da422dfdf",
  "streamId": "urn:lo:nsid:lwm2m:simulator",
  "timestamp": "2022-04-11T12:03:58.695Z",
  "model": "twin_json",
  "value": {
    "device": {
      "0": {
        "deviceType": "Demo",
        "utcOffset": "Z",
        "serialNumber": "LT-500-000-0001",
        "timezone": "Etc/UTC",
        "memoryFree": 6278,
        "errorCode": {
          "0": 0
        },
        "supportedBindingAndModes": "U",
        "manufacturer": "Leshan Demo Device",
        "currentTime": "2022-04-11T12:03:58Z",
        "batteryStatus": 6,
        "memoryTotal": 19400,
        "modelNumber": "Model 500",
        "hardwareVersion": "1.0.1",
        "firmwareVersion": "1.0.0",
        "softwareVersion": "1.0.2",
        "batteryLevel": 44
      }
    }
  },
  "tags": [
    "lwm2m-simulator",
  ],
  "extra": {},
  "metadata": {
    "source": "urn:lo:nsid:lwm2m:simulator",
    "group": {
      "id": "root",
      "path": "/"
    },
    "connector": "lwm2m",
    "network": {
      "lwm2m": {
        "ep": "urn:lo:nsid:lwm2m:simulator"
      }
    }
  },
  "created": "2022-04-11T12:03:58.725Z"
}

This message is generated by the urn:lo:nsid:lwm2m:simulator lwm2m endpoint and embed a twin_json representation of some device instance 0 attributes (reported values).

DataMessage TWIN_JSON format

A TWIN_JSON data message is a JSON representation of reported values that include camel case human-readable entity names.

In a TWIN_JSON data message, each value is embedded in an object, plus an attribute container.

Reminder: Object, Attribute definitions are part of the TwinModel.

For a simple attribute the JSON message will be generated according the following design:

camel case name of the object,
pathSegment id of the object,
camel case name of the attribute,
reported raw value of the attribute.

For example, for a given [/3/0/1, /3/0/9] reported values, associated twin model definitions are:

Object 3 : Device - Instance 0
Attribute 1: Model Number.
Attribute 9: Battery Value.

Related TWIN_JSON of these values will be:

{
  "device": {
    "0": {
      "modelNumber": "Model 500",
      "batteryLevel": 44
    }
  }
}

DataMessage metadata enrichment

A Twin data message as other LiveObjects messages, may embed some metadata.

They are extracted from reported values.

Currently, extracted metadata are:

Metadata Description Source Target

Metadata	Description	Source	Target
location	location of the device	`\6\0\0` to `\6\0\3` Object `6` : `Location` - Instance `0` Attribute `0`: `Latitude` Attribute `1`: `Longitude` Attribute `2`: `Altitude` Attribute `3`: `Radius (Accuracy)`	see `location provided by the device` chapter

location

location of the device

\6\0\0 to \6\0\3

Object 6 : Location - Instance 0

Attribute 0: Latitude
Attribute 1: Longitude
Attribute 2: Altitude
Attribute 3: Radius (Accuracy)

see location provided by the device chapter