1.2 The Birth of the Architecture Model
While this change in approach to the development of one major avionics system was taking place, the airframe manufacturer that needed the system was wrestling with an even broader problem—that of multiple system integration. Because land-, sea-, air-, and space-based vehicles are now filled with complex interacting systems, the problems of handling this complexity have moved up a level from subsystems within a system to systems within a vehicle.
The issues at this level have a different nature, however. The total vehicle with all its embedded systems may be considered to be one supersystem. The power of modern technology can allow unconventional partitionings of this supersystem. Many previously separate functions might be included in one system, or functions that traditionally have been performed by analog processing might now be done digitally. The resulting systems must fit into a well-defined physical structure, interconnected by communication buses with rigid protocols, and they must meet many requirements beyond their basic functionality, such as safety, reliability, and maintainability. Frequently, the systems will be developed by different contractors, so the issue of precise interface definition becomes paramount.
This scenario, in which functional requirements at one level must be rigorously allocated to a physical structure with nonfunctional requirements added, gave rise to the architecture model, described in Parts IV and V.