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FOI Support
Some design decisions about FOI support in SensorHub.
Sensor and other data producers can send two types of FoI events:
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NEW_FOI to notify that a new FoI is being targeted. The event can carry the feature description by reference or at least the feature ID, as well as the time at which the feature starts being observed.
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END_FOI to notify that the FOI is not observed anymore.
NEW_FOI events typically trigger storage to save the Feature description (only simple feature supported for now) if it's the first time the feature has been seen. For next occurrences, only the feature ID is used to map to an existing feature.
The FoI ID is not included in each DataEvent (for efficiency) so the storage also has to prepare doing the necessary indexing on receiving the FoiEvent. All further measurements are to be associated with the latest FOI notified.
In PERST storage implementation, each FoI is associated to a list of time periods during which the FoI was observed.
FoI are also made available from the SOS service implementation:
A new FoI can be added through InsertSensor, InsertObservation or InsertResultTemplate request. In all 3 cases, the SOS implementation needs to be associated to a feature storage so that the feature description can be persisted.
The current SensorML description will include only the last FOI being currently targeted by the sensor.
When generating a snapshot SensorML, the XML can include all the FOI targeted during the time period defined in validTime.