Ken M,
Any system that is designed to react to nothing more than current input conditions is nothing more than a mechanical switch handler.
You might as well revert to the days when all automated mechanical activity was based on the state of a set of mechanical toggles.
In doing so, you are not taking advantage of sensory input in terms of the product being processed!
At the very least, responding to a particular signal, one that might be logically out of sequence, might potentially create a bad, if not worse, situation!
Any "SMART" System should KNOW how a process should unfold. If it doesn't unfold as expected, then, in terms of the processor, that should be a "cause-to-pause"!
How can a Processor KNOW anything??? The processor should be comparing the unfolding activity to the expected activity described in a model of that activity! If there is a discrepancy, there is a problem. It's that simple.
The "model", that is, the expectation, should be "coded in".
It's called... Human Think!
If you are controlling a system manually you can clearly see when things are not unfolding as they should. In doing so, would you ignore the fact that something is unfolding wrong??? Of course you wouldn't! You would, or should, STOP the process rather than continuing to run only making matters worse!
Do you have any idea what I'm talking about? I can explain further.