Created question in FIWARE Q/A platform on 23-02-2016 at 13:02
Please, ANSWER this question AT https://stackoverflow.com/questions/35578078/can-a-derived-event-be-used-as-an-initiator-for-a-temporal-context

Question:
Can a derived event be used as an initiator for a temporal context?

Description:
I am trying to have a derived event trigger an AbsenceEPA, by having the associated temporal context be initiated by the said derived event. Is that possible? This is the configuration I have:

{
"epn":{
"events":[
{
"name":"PollingCount",
"createdDate":"Fri Feb 19 2016",
"attributes":[

{ "name":"restaurantId", "type":"String", "dimension":"0" }

,

{ "name":"pollCount", "type":"Integer", "dimension":0 }

]
},
{
"name":"PrinterContextUpdate",
"createdDate":"Fri Feb 19 2016",
"attributes":[

{ "name":"restaurantId", "type":"String", "dimension":0 }

,

{ "name":"lastTimestamp", "type":"String", "dimension":0 }

,

{ "name":"entityId", "type":"String", "dimension":"0" }

,

{ "name":"entityType", "type":"String", "dimension":0 }

]
},
{
"name":"PrinterStoppedPolling",
"createdDate":"Tue Feb 23 2016",
"attributes":[

{ "name":"restaurantId", "type":"String", "dimension":"0" }

,

{ "name":"lastTimestamp", "type":"String", "dimension":0 }

]
}
],
"epas":[
{
"name":"CountEPA",
"epaType":"Aggregate",
"context":"CountCompositeContext",
"inputEvents":[

{ "name":"PrinterContextUpdate", "alias":"pp", "consumptionPolicy":"Consume", "instanceSelectionPolicy":"First" }

],
"computedVariables":[

{ "name":"Count", "aggregationType":"Count", "pp":"1" }

],
"evaluationPolicy":"Deferred",
"cardinalityPolicy":"Single",
"internalSegmentation":[],
"derivedEvents":[
{
"name":"PollingCount",
"reportParticipants":false,
"expressions":

{ "restaurantId":"ArrayGet(pp.restaurantId, ArraySize(pp.restaurantId) - 1)", "pollCount":"Count" }

}
]
},
{
"name":"PrinterStoppedPollingEPA",
"createdDate":"Tue Feb 23 2016",
"epaType":"Absence",
"context":"SentLastPoll",
"inputEvents":[

{ "name":"PollingCount", "alias":"pc", "consumptionPolicy":"Consume", "instanceSelectionPolicy":"First" }

,

{ "name":"PrinterContextUpdate", "alias":"pu", "consumptionPolicy":"Consume", "instanceSelectionPolicy":"First" }

],
"computedVariables":[],
"evaluationPolicy":"Deferred",
"cardinalityPolicy":"Single",
"internalSegmentation":[],
"derivedEvents":[
{
"name":"PrinterStoppedPolling",
"reportParticipants":false,
"expressions":

{ "restaurantId":"pc.restaurantId", "lastTimestamp":"pu.lastTimestamp" }

}
]
}
],
"contexts":{
"temporal":[
{
"name":"CountTemporalContext",
"type":"TemporalInterval",
"atStartup":false,
"neverEnding":false,
"initiators":[

{ "initiatorType":"Event", "initiatorPolicy":"Ignore", "name":"PrinterContextUpdate" }

],
"terminators":[

{ "terminatorType":"RelativeTime", "terminationType":"Terminate", "relativeTime":"90000" }

]
},
{
"name":"SentLastPoll",
"createdDate":"Tue Feb 23 2016",
"type":"TemporalInterval",
"atStartup":false,
"neverEnding":false,
"initiators":[

{ "initiatorType":"Event", "initiatorPolicy":"Add", "name":"PollingCount" }

],
"terminators":[

{ "terminatorType":"Event", "terminatorPolicy":"First", "terminationType":"Terminate", "name":"PrinterContextUpdate" }

,

{ "terminatorType":"RelativeTime", "terminationType":"Terminate", "relativeTime":"60000" }

]
}
],
"segmentation":[
{
"name":"CountSegmentationContext",
"participantEvents":[

{ "name":"PrinterContextUpdate", "expression":"PrinterContextUpdate.restaurantId" }

]
}
],
"composite":[
{
"name":"CountCompositeContext",
"temporalContexts":[

{ "name":"CountTemporalContext" }

],
"segmentationContexts":[

{ "name":"CountSegmentationContext" }

]
}
]
},
"consumers":[
{
"name":"alert",
"createdDate":"Fri Feb 19 2016",
"type":"Rest",
"properties":[

{ "name":"URL", "value":"http://api-dev.priorhq.com/polling_monitor" }

,

{ "name":"contentType", "value":"application/json" }

,

{ "name":"formatter", "value":"json" }

,

{ "name":"delimiter", "value":";" }

,

{ "name":"tagDataSeparator", "value":"=" }

,

{ "name":"dateFormat", "value":"yyyy-MM-dd HH:mm:ss" }

],
"events":[

{ "name":"PollingCount" }

,

{ "name":"PrinterStoppedPolling" }

]
}
],
"producers":[],
"name":"Prior"
}
}

The derived event is PollingCount and the temporal context is PrinterStoppedPolling.

Thank you.