Ignition theory

[James Montebello]

I'm sure everyone on this list is familiar with the idea that
ignition advance increases with engine speed.  However, a number
of the newer ignition systems take load into account to alter
the timing.  I would suppose that one retards as load increases 
(wild guess there).  Any general relationships?  Most of the 
systems I've seen use throttle angle to indirectly measure load.
Is it likely they take a rate of change into account as well?
If so, what would be the general behavior for a given rate of
change?

Just trying to get a discussion going...

james montebello