. There are two types of channel objects: CommandChannels and
NotificationChannels. The former is responsible for receiving
commands from a middleware while the later is responsible for
communicating to a middleware asynchronously. Several
Source objects can be associated to a NotificationChannel. The
message received through NotificationChannel is called
Notification Message. Successively getting Notification
Message can be treated as a Notification-cycle. After creating
and configuring NotificationChannel middleware receives
Notification Message asynchronously that contains tag list
grouped by Source objects.