Welcome to the ARIA Project.
ARIA streamlines setting up of a network based public addressing system in an organisation. It uses the Asterisk Telephony server at the back and uses SIP/RTP protocols for data transfer.
ARIA server doesn't do any magic of itself. It is simply an abstraction of the asterisk paging system so that users can manage it without messing with the asterisk configuration scripts.
See also: Aria Client.