A collection of field names that identify the observation values the server should return. This property instructs the service to return a subset of values when pushing observations to the client. Restricting the values returned will limit the amount of memory required to store individual observations and therefore reduce the memory footprint of the application.
The default is an empty MutableListImpl, which returns all observation fields from the server.
The output fields take effect when connecting to an empty DynamicEntityDataSource. The following three steps are required to modify the output fields for an existing connection: DynamicEntityDataSource.disconnect(), DynamicEntityDataSource.purgeAll(), and DynamicEntityDataSource.connect().
Note that the geometry, track ID (if available), and timestamp fields are always included with each observation.