Ventana software support forum

I described Instant Manual briefly last spring, and got several as-yet unfulfilled requests for it. This is because the manual was incomplete, and I wanted to finish it. This has now been accomplished. Some years ago, while reading the STELLA manuals, it became clear to me that I needed a similar wa...

I have appreciated the comments re CLD vs SD diagrams, techniques, descriptions of numerical analysis, etc., and their relationships to working as a consultant with clients. This is out of my universe, and it is quite interesting and illuminating to eavesdrop on these discussions. I am a teacher, ho...

Paul Kucera presented a simple stock-flow diagram. Here is an expanded version: > Stock-Flow the representation of system levels (states or accumulations) as > boxes with the pipes containing valves used to show the things > that change the levels. > ___________ > | | > Source ----X----->| Level |--...

This conversation on feedback has been extremely useful to me! During a visit to MIT and Albany last December, I talked with JWF and GPR about some of the issues of applying SD to biology and medicine. In looking through some of the D-files I found references to some of the different viewpoints of e...

Re SD0250: fermentation processes Jaime - At the risk of providing just a me too comment here, I would agree with Andy Ford that a model of eutrophication of lakes would have a great deal of similarities with your problem. This illustrates one of the great under-utilized advantages of system dynamic...

John Sterman provided an elegant answer to my feedback question. Thanks! My first response was Duh! Of course! Then I pondered: why was there any confusion on my part about this at all? I have read Forresters Intro, Goodmans notes, and Richardson and Pugh; its not like I never saw this before. On th...

In SD-0228, George elaborates further on feedback and feedforward concepts, and the varying interpretations of these concepts by social scientists, engineers, and system dynamicists. Of course much more detail is provided in his recent book as well. We all know that teaching forces us to examine fun...

Gene - I like the online University idea! Really But suppose we dont worry for now about credits and grants. >I have a feeling there is more than sufficient talent, frustrated with their >current environment, poised just waiting for an opportunity to do this. I dont know if this is correct, but I ha...

Re Roderic Gills comments:

I have heard Jay Forrester on several occassions, (approx):

"Youll never convince your colleagues; dont worry about it; teach the
students, and outlive your colleagues."

ed gallaher
gallaher@teleport.com

In a recent message Dr. Gill provides every possible communication channel -except- an e-mail address! As Bob E. has pointed out, many mail readers strip this information from header. I find it in the header most of the time, but not this time. Id like to correspond with R.A.G. outside the list; wha...

Re SD success, why not more over? Dr Roderic A. Gill writes: >students may have liked it ...academic colleagues considered >my activities to be something akin to a mix of heresy and witchcraft >But I am a cynic. Is one paranoid when someone -really is- out to get you? >....And a mindset is the harde...

>Gene Bellinger; CrbnBlu@aol.com said: >Would it not make much more sense to find people with nagging problems and >then develop their understanding of a technique for understanding and dealing >with the problem. In this fashion they would find immediate value in the >technique as opposed to being t...

Augusto Carena asks: > >Why - if true - System Dynamics, in nearly four decades, did not exploit >(both in universities and in business) all the enormous potential that many acknowledge and we practitioners feel? Is this a local problem (we work in Italy) or a more generalized one? > > >If you think...

>Date: Wed, 1 May 1996 11:04:06 -0700 >To:e1sad@ice.csv.warwick.ac.uk (Adrian Boucher) >Adrian Boucher wrote: >> In schools we have a so-called >>National Curriculum which is deemed to contain all that is needed to >>become suitably educated for the modern complex world. >>Unfortunately, it doesnt a...

>In SD0131 Shaun TANG discussed diffeq and SD Please look at Shauns original message to obtain the terminology. I wont repeat it here. Shaun, I found your sorting into type P and Q to be interesting and though-provoking. I agreed with most of what you said, except: >Theoretically, type P problems sh...

>Another recent example is the work by Bob Johannsen from >Portland State University using stock-and-flow modeling to help deal with >the problems at the Multnomah County Sheriffs Office. I havent worked to any extent on this problem, but I did sketch out a model about 6 months ago after reading an ...

>Jim Hines said to Jay Forrest: > >I think you are right that SD has grown sometimes faster and sometimes >slower. And my perception is also that the last decade has seen a >rapid increase in interest. (As good SDers, of course its hard for us >to say whether this is due to an increase in the **rate...

>William Steinhurst wrote: >SD is >fundamentally a continuous analysis using a discrete numerical method >to find the solution. Before calculus, answers were obtained by adding up all the little bits and pieces. At best these provided estimates of the "real" answer. This process was very t...

>On Wed, 24 Apr 1996 George Richardson wrote: >> Eds point is that simulation allows more people access to such models. > >This is just the aspect of SD that first attracted me. Me too! Ill have more to say on this in the future, but right now Im going to mostly mull all this over. With one exceptio...

>irt: gallaher@teleport.com (Ed Gallaher), Mon, Apr 29, 1996 6:32 PM EST >When I forget that I am a student I seem to enter periods during which >not much learning happens. There are also times when searching results in no >answers at all and it is better just to be still and allow the answer to fin...

4/30/96 John Edwards says: >I have a simple suggestion about Eds problem of "what to call it" >for K-12 classes. Ed, as long as what you want to do in these classes is >clearly a subset of system dynamics (defined as you wish), then just >call it system dynamics. I believe you are right! I...

> Evolution proceeds by sequential >expansions and contractions. SD has expanded for at least ten years and a >contraction could do much to create greater cohesion in the field and >prepare SD for a more robust and potentially meaningful expansion! I hadnt really thought of it this way, but I believ...

>I think restricting the term "system dynamics" in the way you suggest will >cause a great deal of confusion. >Jim Hines Thanks for your reply. I am not necessarily pushing for a restriction of the term "system dynamics", but I am looking for A NAME that makes sense. In a k-12 ed...

>On Tue, 23 Apr 1996, Ed Gallaher wrote (among other things): > >[...] >> I did see the articles in Science. However, these papers described >> differential equations and not SD models. This is not a trivial >> difference! >[...] In a thoughtful reply George Richardson commented: >In fact, a system ...

>As I understand it, the fundamental difference between discrete and >continuous has to do with how the simulation schedules its run. >Does this help? Actually, not too much. Reverting to my dyed-in-the-wool applied perspective, I believe it would be more useful to describe -problems- which are cont...