Ventana software support forum

Kim,

Many good ideas here and I hope they get an airing to take us forward.

Another is to make conference papers available on CD for those who cannot
get there.

Not sure about Seychelles - whats wrong with Wigan or Oberhausen?

Geoff
From: "Geoff Coyle" <Geoff.Coyle@btinternet.com>

Well, my innocent little attempt to help a student in distress has triggered off a bit of a storm. George Richardson and Nelson Repenning both tell me that the proper formulation is a table function. Maybe it is or maybe not and, as my good friend George suggests, it is a matter for debate and beer ...

The growth of system dynamics in the United Kingdom has been considerable in the past couple of years. There are now about 80 Society members in the UK and three annual gatherings of people interested in system dynamics have attracted a strong attendance. It therefore seemed that the time might be r...

Jim Hines sent a very helpful comment on my negative levels note. Its very agreeable when a colleague goes to such trouble and we could clearly have a very nice debate on this. Jims message was: >Your formulations are very nice. But, isnt it **usually** true that >non-negativity formulations involvi...

Folks, I did send a correction but some people seem not to have received it about the conference on system dynamics and defence. the contact address is saunders@ndu.edu. Regards, Geoff geoff.coyle@btinternet.com Professor Geoff Coyle Consultant in System Dynamics and Strategic Analysis Tel: (44) 017...

Dear All, A conference on system dynamics applied to defence is being organised by the National Defense University in Washington DC for about 2-3 days in the week commencing May 15. For more information please contact Dr John Saunders at saunders@nde.edu. Regards, Geoff geoff.coyle@btinternet.com Pr...

You are absolutely right to do the thinking before the modelling!!!!! When I run my one-week intensive SD course I fund that the participants always turn on their computers before I even start talking. I then make them turn them off as we are going to spend the first two days thinking about problem ...

Dear All, Just in case some of you dont know, the UK Chapter of the Society is having its annual meeting on February 3/4 in the spa town of Harrogate. The theme is SD in Consultancy with speakers from HVR-CSL, Cognitus and McKinsey. We also hope to present the Chapter prize for the best project in S...

This doesnt answer all your points but there is a lot on validation in my 1996 book, which also has lots of case studies of modelling. See also a forthcoming paper Validation of Commercial System Dynamics Models, which will appear in SDR early next year. Regards, Geoff geoff.coyle@btinternet.com Pro...

This is a very interesting reply. I ABSOLUTELY agree with the need to examine all variables fairly regularly. It is simply impossible to debug a model and to be sure that it is doing the same things as the real system and for the same reasons just by looking at a few graphs. it is also good practice...

This is interesting stuff but Id like to know what questions you hope to answer with your model. Richardson and Pughs textbook makes the point very well that a model should be a simplification of reality designed to answer some reasonably well-designed questions. They also state that an acid test of...

Jose, Yes, of course, this has been done but not by mixing two different types of software, it has been done perfectly well in DYNAMO format languages. It has been done in several different domains, not just production. References (some of them) are: Modelling the discrete ordering of hydro-electric...

"j-d" is right to remind us of the vital importance of the Why question as opposed to the tricks of coding. ANY model has to be designed to answer questions or be fit for a purpose. the test of the goodness of a model is how well it meets its purpose though, as Richardson and Pugh profound...

Thats easy. Just create two levels for average income, smoothed over, say, 6 and 12 months (or whatever periods you choose, though be careful about DT). Have an auxiliary for the difference between them and, depending on whether the auxiliary is positive and negative, Bobs your uncle, as we say. In ...

Dr Nirumand, Interesting question. Yes, SD is very useful for certain types of forecasting. There is a discussion in my firs t book, Management System Dynamics, John Wiley, 1977. The book is long out of print but there may be one in your library. You might also contact Dr Rocky Ansari, Vali Asre Ave...

Bullwhip effects also occur within businesses. My book uses the case of the Domestic Manufacturing Company, based on a consultancy assignment with a white goods manufacturer, in which the bullwhip is very pronounced. The problem is modelled both qualitatively and quantitatively, policies are redesig...

I have noted the message from David Lane about the UK Chapter. In reply, I can only say that the Chapter was set up exactly as the Society was when it first started. The proponents took the full advice of the Societys President and Secretary and the Vice President for Chapters. As the Societys rules...

Ms Wolter, The purpos of SD is to represent differential equations as flows. If you like, the theory of system dynamics IS the algorithm you are looking for. Your equation (birthrate-deathrate)*population illustrates the problem of correct thinking. If POP is population, BR and DR are birth and deat...

Dear Colleague, I dont understand WHY you are trying to build this vast model. What is the reference mode for the problem? A model is supposed to be a simplification of reality intended to be a tool for thinking with. Richardson and Pugh say that it should be designed to answer a set of well-chosen ...