Ventana software support forum

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Justin I have a more pragmatic definition of system dynamics: It is a set of equations calculating the values of different variables Xi i = 1. n at different period of time: Xi(t) = Fi (Xj(t),exogenk(t),paraml) j in...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi everybody Jim Hines writes < the only defining characteristic of SD work is an interest in how < structure creates behavior. What does creates mean? Does it mean 1.. Has an influence 2.. Has a determinant influence ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> I agree with Finn, but unfortunately finding the causes and the level of their implication is the principal difficulty of SD, and I would say of most of the problems of our world. Give me the way to know the causes of ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Martin I have not the pretensionsness to help you in this difficult matter but your query can still be studied methodically. <We urge SD students to model a problem, not ""the system""; the (ment...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi The high number of parameters is not peculiar to this model. When I built most of my models, I experienced the same kind of difficulty. The influence diagram was easy to build, and looked credible, the equations wer...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hello Fadl Some things must be checked. First in the test inputs. I suppose there are several real time series corresponding to several variables of the model in each input test. Have the test inputs the same correspon...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi every body. Thank you to all people that answered my question. It gives me a better idea of the intention behind the formula : all models are ... Just two remarks: When I started in the business, being a scientist, ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> WAS: REPLY Strategy magazine article about Jay Forrester Hi every body Bruce Skarin writes: < One of the reasons System Dynamics is so unique as an approach to problem < solving is that it recognizes its faults before ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Francisco. I have more or less the same problem. It is like dynamic programming in O.R. One has to take decision every time step. This decision depends on the past events and on future events that are stochastic. So...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi John, You can find on the Vensim forum system dynamics subject a simple model that I have starded on the subject. But by lack of time, I have not checked it completely. So it has probably bugs in it, or the equation...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Mark It is just after having worked hard on trying to simulate short term price setting on a model based on days, that I decided to leave it for the moment aside, and explore the alternative of setting up the right ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Bill You wrote on my remark >> I said that business people understood the concept of feed back, >> but never pretended that they understood their implication, >> particularly when there are many of them. >> We rely ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi everybody At least having not convinced any body I brought some animation to this list, which due to the character of the field is not an easy matter! Now about what I wrote. John Gunkler writes about what I wrote: ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Joel Rahn writes <Jean-Jacques Laublé apparently prefers to use Vensim (which is not the <same as SD) in order not to develop SD models I do not see where I wrote that, I wrote exactly the contrary. I start with a simp...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> [ Was Feedback and Behavior (SD5408) ] John Voyer writes > I think the reason is that managers so poorly understand the integration > that goes on in stocks and flows that the resulting dynamics are revealing > to them...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Foster. When I build a model, I always start with a no stock, no loop model, unless the necessity to have one stock is evident. It looks then like a common influence diagram. It is only driven by exogenous variables...

Posted by =?Windows-1252?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Geert Thanks for your references. Two remarks. The particularity of non storability of services works too for some kind of productions: example to order productions. Generally people that work on order, have to wa...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Ahmet Thanks for replying. You seem to be describing what we call in France a tour operator, who organizes travels, using subcontractors. It does not deliver the service and is more then an pure intermediary as it l...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Francisco I asked a question called 'Aggregation techniques' the 16-1-2005 which summarizes approximately your question. It generated many answers that you can consult on the web site archives of the sd mailing list: h...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Alan You write that there are plenty of models dealing with planning production processes. But unfortunately I never saw any model dealing with planning services where there are no inventories. The main difference b...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Justin. Thanks for answering my e-mail. Can you give some references about your architectures based on resource mapping ideas, like articles, books, software, web site? My principal difficulty but I think it must be...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Francisco I have never seen any model or paper dealing with planning and utilization of resources. I have worked for about three years with planning the utilization of our car fleet on a day to basis trying to 'opti...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> There is a Web site named http://www.evolvinglogic.com supposed to explain the ideas behind the article in S.A. and that is probably selling something but I do not know what. I tried to understand what is meant by RAP ...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi Erling. I think that there will never be a definitive answer to your question, because it depends on the problem you are working on. The tendency is always to generalize something that has worked on something to eve...

Posted by =?iso-8859-1?Q?Jean-Jacques_Laubl=E9?= <jean-jacques.lauble@wanadoo.fr> Hi There is a paper from the late SD conference in Oxford called Developing system dynamics models from C.L.D. from Thomas Binder If you are a bit accustomed to modern mathematics formulation, it should give you intere...