Ventana software support forum

Hi Dear

I am really new in system dynamics concepts and Vensim. I am really confused and struggling to make clear understanding of loop formation. Could you please see my attachment and confirm me whether this small model does have any loop? To me, it has two loop. is it right? If it is so, are they following system dynamics rules?

Any reply will be appreciated.

Hi Dear!

I know it's a Christmas Time but I am expecting answer of my simple question in my previous post.

Please..


Tasnuba

I would agree that there are two loops. I don't remember seeing any specific "rules" anywhere for SD though. The most important part of modelling is that the model works and helps you understand the problem you are trying to solve.

Have you been through the PLE tutorial at the following address?
http://www.public.asu.edu/~kirkwood/sysdyn/VenPLE.pdf

Hello

You certainly have two feedback loops in your model. You have a positive feedback loop going from Bank Money to Interest and a negative feedback loop from Bank Money to Withdraw. I would suggest that the Rate and Rate Withdraw be values less than 1. Actually, they are probably much less than 1.

If you are new to the field and really interested in learning system dynamics, I would recommend John Sterman’s Business Dynamics: Systems Thinking and Modeling for a Complex World.

I certainly hope this makes sense.

Best,
Rod MacDonald

There are lots of other resources here,
http://vensim.com/resources/

The Road Maps series might be of particular interest.