Apart from simple strings such as "22.5" or "yellow", you can use complex structures as attribute values. In particular, an attribute can be set to a vector or to a key-value map (usually referred to as an "object") using updateContext (or equivalent convenience operation). These values are retrieved with a queryContext on that attribute (or equivalent convenience operation) and notifyContext notifications sent as a consequence of a NGSI10 subscriptions.
Vector or key-map values correspond directly to JSON vectors and JSON objects, respectively. Thus, the following updateContext request sets the value of attribute "A" to a vector and the value of attribute B to a key-map object (we use UPDATE as actionType, but this can be used at initial entity or attribute creation with APPEND).
(curl localhost:1026/v1/updateContext -s -S --header 'Content-Type: application/json' \
--header 'Accept: application/json' -d @- | python -mjson.tool) <<EOF
{
"contextElements": [
{
"type": "T1",
"isPattern": "false",
"id": "E1",
"attributes": [
{
"name": "A",
"type": "T",
"value": [
"22",
{
"x": [
"x1",
"x2"
],
"y": "3"
},
[
"z1",
"z2"
]
]
},
{
"name": "B",
"type": "T",
"value": {
"x": {
"x1": "a",
"x2": "b"
},
"y": [
"y1",
"y2"
]
}
}
]
}
],
"updateAction": "UPDATE"
}
EOF
The value of the attribute is stored internally by Orion Context Broker in a format-independent representation.
Note that (for API version 1) in order to align JSON representations, the final "leaf"
elements of the structured attribute values after traversing all vectors
and key-maps are always considered as strings. Thus, take into account that
although you can use for instance a JSON number as a field value in updates
(such as {"x": 3.2 }), you will retrieve a string in queries and notifications
(i.e. { "x": "3.2"}).
In API version 2, the final "leaf" elements of the structured attribute values after traversing all vectors and key-maps uses the right native JSON type (number, boolean, etc.). Thus, take if you use for instance a JSON number as a field value in updates (such as {"x": 3.2 }), you will retrieve also a number in queries and notifications (i.e. { "x": 3.2}).