[Martin Taylor 970102 15:30]
Bill Powers (961224.1145 MST)
Bruce Abbott (961224.1310 EST)--
Happy New Year to all.
> Martin's elegant contribution
>was to suggest that in this case the CV would be "stabilized" but not
>controlled.
>Rick's response was to deny that the distinction Martin was making between
>"stabilized" and "controlled" was useful. CV, he said, either is
>controlled or is not controlled.I would tend to agree with Rick, because of my definition of control given
above.
This may be out of date by now, but anyway...
It seems to me that if one wants to discuss (or demonstrate) whether under
some circumstances an environmental function of observables (CEV, for short)
stays stable, and wants to discuss (or demonstrate) that these circumstances
do (or do not) require the existence of perceptual control, then it is
helpful to use different words for the stabilization of the CEV and for
the existence of perceptual control.
It's hardly useful to have arguments of the form
"Under these circumstances the CEV hardly changes its value."
"Under your circumstances, it's not control, and the disturbance isn't
really unknown."
"I know it's not control, and I know the CEV will be stable in the absence
of control only if the disturbance is well modelled."
"Then it's not control."
"I know it's not control, but nevertheless under these conditions the CEV
hardly departs from its nominal value."
"If the CEV is controlled, it has to be by _perceptual_ control, and I'll
demonstrate this by showing that _perceptual_ control works to control
the CEV." "...(!)"
It's so much easier to be able to say that (if you believe so) "The CEV is
stabilized, and it's done by an outflow model."
And to be able to make the rejoider:
"Your stabilization won't work if the disturbance has much unmodelled in it.
If there's much unmodelled about the disturbance, you'll need _control_
to achieve _stabilization_."
Don't you think we would all (or most of us) agree with this latter
statement, and then we could get on with finding out whether in any particular
_real-life_ circumstance some aspect of the probable disturbance might
perhaps be modellable? And if so, whether to do so might aid stabilization
both without _and_ with control?
Remember that as far as the observer is concerned, what is controlled
is ONLY the CV. The idea that this CV is represented by a perceptual signal
inside the other system is theoretical. We can observe CV, but not p. When
we apply a disturbance, we apply it to CV, not to p. The action that opposes
the effect of the disturbance acts on CV, not p. The Test does not involve p
at all. It involves only observables -- i.e., the observer's perceptions.
One might say: "Of course", but what would be the point? We are discussing
a model called PCT, aren't we? In that model, the controlled variable is
a theoretical entity called a perception. In no real world can we determine
for sure what that perception determines as a _controlled_ CEV (i.e. a CEV
whose stability is due to the fact that its defining perception is controlled).
But we can come close, using the Test to determine a CEV, determined by the
_analyst's_ perception, that is a highly correlated with the actual
controlled CEV as the experimental conditions permit.
···
-----------------
Bill,
If you program your randomly interlinked environment, may I ask two things:
1) make sure that the compute-cycle dt's are short compared with the time
it takes those inter-environmental-variable influences to take effect, and
2) Give a thought to programming it is Java.
On (2), I've been trying out Java, inspired by Rick, over the holiday, using
the free Java Development Kit from Sun (http://java.sun.com). There are kits
or links there for various Unix platforms, PCs (I'm not sure about DOS, but
various kinds of Windows), and Macs. Programs developed using the JDK should
be compatible across platforms (which seems not to be true for programs
using the Microsoft development kit). I had a notion to try to rewrite
Simcon, but my skills are as yet inadequate. I've made a neural net node
class that is intended as a generic perceptual input function, but that's
my sole success so far. All the same, I feel Java is a rather easier
language to write in than C or Pascal, once one gets the hang of it.
If the randomly linked environment is made available as a set of Java classes,
with or without source code, on the CSG Web Server, we could all use it as
part of a test suite.
What say you, Rick? And would you contemplate making your classes (and
better, your source code) available to be built on?
Martin