control defintion

i. kurtzer (960125.1600)

This is really neat. I've been reading the posts and sending this one from the
Web. I am impressed; great job Gary!
Now to the point maybe trivially obvious but troubling to myself.
In defining control the current means is by some determining the gain of the
system--though i would prefer some method independent of characterizing the
system--but the gain of any real control system is a function of its bandwidth.
Clearly gain is variable over a frequency range. So the question is is there
another function which could characterize gain across frequencies and would
this not be a better measure?
i.