Ventana software support forum

The signoff on my last note that ended

>...GPR
>embedded in the style of thought in engineering servomechanisms

may be a true statement of the mire of my life, but in fact it was an
unintended result of editing my mail message in a rush. Sorry about that
(but if it gave you a chuckle I guess one shouldnt apologize for the
chance to smile...)


.............................................................................
George P. Richardson G.P.Richardson@Albany.edu
Rockefeller College of Public Affairs & Policy GR383@Albnyvms.bitnet
State University of New York at Albany 518-442-3859 (fax:442-3398)
.............................................................................

I would like to support George Richardsons comments but also go a
little further.

Understanding the intellectual linkages of system dynamics is not simply
to become involved in the heritage industry; one can and should be aware
of the past without being shackled down by it. However, awareness of the
ideas that constitute and define the field of system dynamics also helps us
to locate our subject in the wider movement of systems science, systems
thinking and operational research. I am very aware that some in the field
of system dynamics are wary of any engagement with other disciplines. Yes,
Forrester stepped away from OR in founding the field - and with very good
reason. Yes, much of what was going on in the systems movement when system
dynamics was created looked like airy fairy rubbish and simply annoyed
those of us interested in solving practical problems and in trying to
improve the world a little.

But.

To a large extent these judgements are no longer correct and are
damaging to system dynamics. Working in the UK I get to see system
dynamicists through the eyes of those outside the field. What I observe is
that our field is very easily perceived as being closed, supported by a
clique and unaware of what is going on elsewhere. I know that this is
unjust but it IS a reaction to our endevours. We need to describe, explain,
yes, perhaps sometimes defend what we do to others. And to do that it is
useful to know the differences and commonalities that system dynamics has
with other approaches.
Almost trivial example. Very often you will hear people say, "system
dynamics is about closed systems, isnt it? But they are boring". Now an
over-gleeful urge to press the endogenous perspective can easily lead a
system dynamicists to say that our models are closed . .. .and that we will
fight the next person who says they are boring! The more constructive
approach - for all parties - involves being aware of the intellectual
history lurking behind the comment. In this scenario the questioner has
misunderstood causal closure with closed boundaries. He/she knows from GST
and other work that closed systems - systems in which no material or energy
crosses the boundary either way - are of very little interest and
relevance; only open system seem to be applicable to interesting real world
phenomena. Now knowing that history, a system dynamicist can say that our
models are indeed open, in this sense - sources and sinks are one easy
proof of this - but take a particular view of information feedback which
seems to be helpful in addressing real problems. This usually makes the
questioner interested, open (no pun intended) and willing to exchange ideas
further. I play out this scenario about every 2 months now. It usually
works and I think that it helps the field of system dynamics. However,
there are many other ways in which we can get into such non-ideal speech
situations, when we run aground on prejudice based on a failure to
understand basic assumptions. We are not learning what other systems
thinkers have to say AND we are not getting more of them interested in
system dynamics.

I have said previously that the first place to go to find out about
these connections is Feedback Thought by George Richardson.
However, at a rather lower level, readers (if that is the right word in
the Internet) might wish to look at the System Dynamics Review, volume 10,
number 2-3 from 1994 called Systems Thinkers, Systems Thinking which
contains a range of papers from inside and outside the field of system
dynamics, considering connections and commonalities.
Finally, the second of this years numbers of the journal Systems
Research will contain a piece:
Lane, D.C. and M.C.Jackson (1995) Only Connect! An Annotated Bibliography
Reflecting the Breadth and Diversity of Systems Thinking.
This is a rapid tour of this very wide field, in terms of 68 books,
collections and articles. After a full reference we comment on each one and
try to locate it within a strand of systems activities. This is an
expansion of a piece read at the Stirling conference, the chief difference
being that there is a new section solely on system dynamics (so we can all
have fun arguing about the 9 entries that I chose to represent the field).

Enjoy!

Dr. David C. Lane
Operational Research
London School of Economics and Political Science
D.C.Lane@lse.ac.uk

David Lane wrote:

(Hosts paraphrase: That system dynamics tends to focus on closed
systems and this gives rise for disagreement.
Hosts note: I think Davids purpose here was to focus on different
uses of terminology and not give legitimacy to an oft cited criticism
of system dynamics.)

This is perhaps a simplistic and well-known (by others) view, but I see
this emphasis on endogenous influences as overall healthy. The healthy
part is that it represents self-responsibility. It says that we believe
the most likely causes of problems (and thus of their resolution) lie
within the system and thus eventually within our grasp. The opposite view,
a focus on exogenous influences, says that our troubles come from outside
and thus may not be controllable by us. That puts us as workers in a
victim role, which usually isnt very productive. (Of course, sometimes
the exogenous influences are _mighty_ powerful.)

As David wrote, this is not to claim that system dynamics is about closed
systems: far from it.

Bill


--
Bill Harris Hewlett-Packard Co.
R&D Productivity Department Lake Stevens Instrument Division
domain: billh@lsid.hp.com M/S 90
phone: (206) 335-2200 8600 Soper Hill Road
fax: (206) 335-2828 Everett, WA 98205-1298

System dynamics models are models of thermodynamically open systems
(energy and information are exchanged between the system and its
environment).

Forrester used the term closed boundary to refer to the focus on
feedback loops. Good system dynamics models are open system models in
the thermodynamic sense but do not rely on exogenous time varying inputs
to create the dynamics of interest.

To avoid the confusion David Lane addressed, we should (correctly) refer
to SD models as open system models that endogenously generate their
dynamics.

John Sterman
jsterman@MIT.EDU