Created question in FIWARE Q/A platform on 24-05-2016 at 12:05
Please, ANSWER this question AT http://stackoverflow.com/questions/37410846/how-to-make-orion-send-notifications-only-when-subscription-condition-is-satisfi

Question:
How to make orion send notifications only when subscription condition is satisfied?

Description:
I have made this subscription but it notifies always a attribute is changed.

curl --include \
--header 'Content-Type: application/json' \
--request POST \
--data-binary '{
"attrsFormat":"legacy",
"description": "Day subscription",
"subject": {
"entities": [

],
"condition": {
"attrs": [
"idEvent",
"Title",
"dFlag"
],
"expression":

}
},
"notification": {
"http":

,
"attrs": [
"idEvent",
"Title",
"dFlag"
]
}
}' \
'http://localhost:1026/v2/subscriptions'

I want that orion notify when any attribute described in the condition is changed AND the condition is satisfied.

Example I have in orion this entitys:

Concert1 (idEvent=Mozart, Title=Mconcert, dFlag=1)
Concert2 (idEvent=Salieri, Title=Sconcert, dFlag=0)

I want that when I made a change to any attribute of Concert1, as the condition is satisfied, it will notify.
In the case of Concert2, as the condition is not satisfied, it will not notify.

Is it posible? what I have wrong in this subscription example?

In the documentation do not said much:

condition: Condition that will trigger the notification. It can have
two optional properties:

attrs: array of attribute names
expression: an expression composed of q, georel, geometry and coords (see "List entities" operation above about this field).

List entities

q: A query expression, composed of a list of statements separated by ;, i.e. q=statement;statements;statement. See Simple Query Language specification. Example: temperature>40.