Ventana software support forum

Regarding the discussion of sensitivity analysis. Most of the discussion (including one of my responses) has focused on the use of sensitivity to put confidence bands around the output of the model. Although I think these responses address the original question, there is another use of sensitivity a...

This is a reply to Alessandro Linos request for information on SD work in financial markets. You might look at my dissertation, available from MIT, titled: __Essays In Behavioral Economics__. The essays all are focussed on finance. The first essay in particular, "A Behavioral Theory of Interest...

Natalie, Your sense that system dynamics has a great deal to contribute to the sad state of our urban environments is on the mark. There has been system dynamics work in this area, beginning with Jay Forresters Urban Dyanamics (1969) and the two volumes of Readings in Urban Dynamics (edited by Mass,...

On Fri, 24 Jan 1997, Robert Glitz <rglitz@erols.com> wrote: >We have had teams of 6-8 in size and, recently, a team of 35, as well as >different sizes in between. With the 35 person group, we did alot of >work in sub-groups, by assigning portions of the modeling effort. Did each sub-group have its o...

Concerning the question why SD is not spreading faster:

"Things that grow like weeds usually are"
(An approximate quote from Swami Chetanananda on this topic).

Jim Hines
jimhines@interserv.com

Kjeld and Syed, I have a question for you: I think you use "flight simulators" to refer to a game in which a team plays simulated competitor(s) and "interactive" to refer to games in which teams play one another. That is, in flight simulators the environment is simulated, in &quo...

Some more ideas about documentation: 1) The journals I keep (now they are now word processor documents, using lots of cut and paste) are very heavy on showing behavior; hypotheses (usually loops) about the causes of the behavior; and tests of the hypothesis (which produce more behavior and more hypo...

In a way our models output IS fuzzy logic, in the following sense. In all SD models the output is numbers. In many (though not all!) cases the numbers are interpretted in a logical sense, rather than in a precise-number sense. So, to describe the output wed say "high", "low", &qu...

On Sat, 28 Sep 1996, saeed@ait.ac.th (Professor Khalid Saeed) wrote: >There seem to be two fortunate principles in SD modeling which make it >quite amenable to representing spatial changes: > >1. Spatial changes occur over time .... [major snip] ... ...... > I must >think harder to conceive other ty...

A new version (1.1) of the molecules is available for free download (http://www.std.com/vensim/molecules.html). This version contains additional structures and some reworked connections between molecules. Also new is an 80-page document describing each molecule. Again, we hope you find the molecules...

Bob Eberlein and I have a "proto-alpha" version of the Molecules up on the Web for free download (http://www.std.com/vensim/molecules.html). A very brief paper and some documentation on molecules is also available at the web site. (Ive included a paragraph description at the end of this me...

To George Backus Could you describe the modeling approach(es) that underlie your work? In particular Im wondering what a "portfolio model" is. Is it a "typical" system dynamics model (i.e. Is feedback central; is it largely endogenous; does it use continuous time; is it determini...

On Fri, 2 Aug 96, bh055@ctc.cummins.com wrote: >I am interested in building a System Dynamics Model that develops a trend >for diesel engine use in the future specifically in terms of unit sales, >emissions requirements, horespower, fuel economy, etc. I then what to use ... Id be happy to explore th...

Miss Melek Pisman, I am sure that you will receive a number of replies mentioning "Desert Dynamics" which is list of essential papers compiled by Anjeli Sastri and John Sterman (JSterman@MIT.EDU). The list contains many (but not all) of the papers that people in the field consider importan...

Miss Melek Pisman, I am sure that you will receive a number of replies mentioning "Desert Dynamics" which is list of essential papers compiled by Anjeli Sastri and John Sterman (JSterman@MIT.EDU). The list contains many (but not all) of the papers that people in the field consider importan...

As David Lane suggested, molecules seem to refer to a class of generic structures slightly below his Abstracted Micro Structures. Abstracted Microstructures are intended to generate a mode of behavior. Behavior is not really the central point for molecules, structural representation is. At one extre...

"Archetype", "molecule", and "generic structure", are terms that are cropping up on this list and should not be confused. 1. An "archetype" is one of the relatively small number of dynamic learnings that have emerged in our field over the past 30 years. Archet...

On Mon, 8 Jul 1996, Jay Forrest <pteragen@neosoft.com> wrote:
> My comments focused more
>on the clients nature and yours more on the problem. I think you will agree
>that in real life both should generally be considered!

Absolutely!

Jim Hines
jimhines@interserv.com

On Sat, 6 Jul 1996, Jay Forrest <pteragen@neosoft.com> wrote: > I use whichever approach [i.e. SF or CLD] >the client is more comfortable with (and to be honest that is often CLD as >stock and flow seems to create some difficulties for some people). Jay, I think the approach a client is most comfort...

On Sat, 6 Jul 1996, Jay Forrest <pteragen@neosoft.com> wrote: >As a chemical engineer I well understand the additional insight provided by >the stock and flow concept of SF over causal loop .... The implication that SF provide MORE insight than causal loop diagrams is not correct. Each kind of diagr...

On Fri, 5 Jul 1996, Jay Forrest <pteragen@neosoft.com> wrote: > "What is a causal loop diagram >which contains formulas and provides graphical output...?" Well, the diagram is a causal loop diagram. The formulas are equations and the output is simulation output. A causal loop diagram is on...

On Thu, 4 Jul 1996, Kim Warren <kim@farthing.stargate.co.uk> wrote: >Youre right - Ive noticed the same, but we absolutely have to crack this >one. Causal loops are completely inadequate for any serious attempt to >model real situations and test policy options. I strongly disagree with the critism o...

My friend Benny Budiman asks about the use of system dynamics in situations where a client has a number of possible explanations for an issue. Problems for which there are a number of potential explanations are tailor-made for what we called the "standard approach" in the applications clas...

I have had clients who find causal loops exciting and who dont find stock and flows exciting. (And, I have also had clients who liked stock and flows, but didnt warm up to loops). But, the problem with stock-and-flow diagrams has never been expressed to me as a problem with being overly academic or ...

On Wed, 29 May 96, bbens@MIT.EDU wrote in SD0281: > I have seen two methods of modeling: >loops and sectors. In loops, the model starts with a description of the >system and its operations in causal loops that represent several key >dynamic hypotheses. In sectors, the model starts with a functional ...