There are many processes, which often require to communicate with several others. If each process had to create a separate connection to all other processes, the number of links would increase quadratically and communication management would quickly become unwieldy. Also, to minimize the impact of future changes in hardware and software architecture, we want to minimize the direct knowledge of system configuration required by each process. This process provides IPC through the mechanism of Unix message queues. This provides each process its only avenue to data and state information.
Any process can request data by sending a request to the mailer via the mailer's message queue.
It then performs a hanging read on its message queue until the requested data is available. This request is restricted as much as possible. Last item the most recent data of this type is requested and provided without delay. In addition to requests, a process may provide an updated data product for the blackboard. This design has many advantages.