<Bob Clark (940724.1358 EDT)>
Bill Leach 940713.23:12 EST)
Your comments suggest that the purpose of my post was not clear.
In discussing TERMINOLOGY, I was concerned with inconsistent usage of
words. An important source of unnecessary arguments, conflicts etc.
is usage of terms, familiar to each participant, but with different
meanings.
This situation is frequently the case in discussions between physical
scientists and those with behavioral scientists.
I began with "Model" because it is very useful. It can be applied in
many situations. However, for our present purposes, it needs some
restrictions. My initial definition of "Model," quoting from Bob
Clark (940704.1355) Subject: RKC-MORE PROG CONTROL was:
*Model
*A Model is a description in terms of one or a combination of flow
*diagrams. ... These diagrams show the pathways that signals follow
*between/among boxes. The boxes represent ways in which signals can
*be modified and/or combined with other signals. Modifications
*include at least the ordinary operations of mathematical analysis
*and symbolic logic.
In the post to which you refer, Bob Clark (940713.1750 EDT) Subject:
RKC - TERMINOLOGY, I was responding to Bill Powers (940705.1430 MDT)
definition of "Flow Diagrams" in the form you quoted.
Your comment about _improper_ _use_ of flow charts in behavioral
sciences is certainly correct. That illustrates the need for
adequate definitions of our terms. For specific applications
suitable qualifiers are needed -- as your further comments suggest.
To be applied to negative feedback control systems, it is necessary
to further qualify these definitions.
In the post on which you are commenting, I was distinguishing between
the definitions of flow chart and of system diagram. I pointed out
that one could be "derived" from the other by changing the treatment
of temporal variables. As presented, neither definition is concerned
with the definition of negative feedback control systems.
You comment:
A control system controls independent of the presence or absence of
disturbances. Disturbances are necessary to apply the TEST and of
course in the real world disturbances are otherwise common but
disturbances themselves are not necessary for control to exist.
Of course. But that was not the point.
In this sequence of definitions, "control," had not yet been defined.
It was defined next. After definition of "control," "control system"
could be, and was, defined.
In my preceding post, Bob Clark (940704.1355) Subject: RKC-MORE PROG
CONTROL, I had suggested:
*Control
*Control is the production of actions in opposition to the acts of an
*external entity.
To _apply_ the term requires using the TEST -- but disturbances are
not included as part of the definition.
You remark:
An additional problem that I see with using a definition that
requires disturbances for control etc
But the _definition_ does not _require_ disturbances. They are only
needed to determine _whether_ _or_ _not_ the term, _control_, is
applicable.
The SUGGESTION to which you reacted was originally from Bill Powers,
(940705.1430 MDT) Subject: Floow Charts vs system diagrams." Your
remark:
I'm not sure what is being said!
is very appropriate. I'm also not sure what he meant, although I did
attempt some comments in Bob Clark (940713.1750) Subject: RKC -
TERMINOLOGY.
Regards, Bob Clark
···
Subject: Floow Charts vs system diagrams" by suggesting a modified