FIWARE IoT Agent Framework: How to define a device with nested attributes in IoT Agent e.g geo:json? - fiware

Question

I can't find how to define a device where its entity contains nested attributes.
The need is to pass gps coordinates from a device to an entity having geo:json (like urn:ngsi-ld:Shelf:unit001 in tutorial https://github.com/FIWARE/tutorials.Entity-Relationships)
Following the https://fiware-tutorials.readthedocs.io/en/latest/iot-over-mqtt/index.html the below
curl -iX POST \
'http://localhost:4041/iot/devices' \
...
-d '{
"devices": [
{
"device_id": "motion001",
"entity_name": "urn:ngsi-ld:Motion:001",
{ "object_id": "c", "name": "count", "type": "Integer" }
],
"static_attributes": [
...
creates the count attribute
{
"id": "Motion:001",
"type": "Motion",
"TimeInstant": {
"type": "DateTime",
"value": "2020-04-04T07:52:29.00Z",
"metadata": {}
},
...
"count": {
"type": "Integer",
"value": "12",
"metadata": {
"TimeInstant": {
"type": "DateTime",
"value": "2020-04-04T07:52:29.00Z"
}
}
},
How to replace the count above in order to get the below outcome ?
"type": "geo:json",
"value": {
"type": "Point",
"coordinates": [13.3986,52.5547]
},
In all examples and documentation the attributes are defined in one level (not nested) https://iotagent-node-lib.readthedocs.io/en/latest/api/index.html.
Tses

Answer 1

Device measures are usually just numbers so for structured elements you either use the expression library or pass data as structured JSON using the IoT Agent for JSON.
That being said, improved GeoJSON support has recently been added to the IoT Agent library, so the following will work on *:latest IoT Agent docker images. According to the Documentation various input formats are now possible.
The defined type of any GeoJSON attribute can be any set to any of
the standard NGSI-v2 GeoJSON types - (e.g. geo:json, geo:point).
NGSI-LD formats such as GeoProperty, Point and LineString are
also accepted type values. If the latitude and longitude are
received as separate measures, the expression
language can be used to concatenate them.
"entity_type": "GPS",
"resource": "/iot/d",
"protocol": "PDI-IoTA-JSON", ..etc
"attributes": [
{
"name": "location",
"type": "geo:json",
"expression": "${#lng}, ${#lat}"
}
] }
For attributes and static_attributes which need to be formatted as
GeoJSON values, three separate input formats are accepted. Provided
the type is provisioned correctly, the value may be defined using
any of the following formats:
a comma delimited string
{ "name": "location", "value": "23, 12.5" }
an array of numbers
"name": "location",
"value": [23, 12.5]
}
an fully formatted GeoJSON object
{
"name": "location",
"value": {
"type": "Point",
"coordinates": [23, 12.5]
}
}
So if your device can send a comma separated long/lat string you should be fine.