4 Basis for a Hierarchy
For a system to be a communication system, it must be composed of two complementary
informative processes. If we are to study a communication system as
composed of more than one function, that is, we choose to treat it as something
other than an indivisible whole, it is necessary to break the larger process into
smaller processes. Central to breaking a process into parts is determining which
descriptions of processes are most natural and best help us describe, predict, and
understand the communication system. In some decompositions, the resulting
sub-processes may appear to be natural, having a reasonable explanation, while
in other cases, the division into sub-processes will appear very arbitrary in nature
with unnatural sub-processes. Obviously, a decomposition that produces reasonable
explanations is superior to one where the boundaries between processes are
arbitrarily chosen.