Implements the communication protocol between the caller and the data
source (notification and agent) based on tags. Implementations are
expected to map the provided attribute name to some aspect of the
notification payload. The later is defined by method prime.
Parameters: tagName - the tag of the attribute the value of which is required
Set the notification to be used as the data source. Load the hashmap
with all of the notification contents. Note that the keys are used
as attribute tags in the mapping resource file
Parameters: n - the notification to be used as data source at subsequent callsof get()