SystemsDynamics

Systems Dynamics Birds of a Feather

Monday, November 3, 2003, 7-9pm

These are MikeMelendez notes, please feel free to add and modify. I hope to create simple jpg images to connect with the definitions, but words will do for now. It would be great if someone could add the problem statement and created diagram.

We read Dr. Seuss' The Lorax and attempted to diagram the problem presented.

Parts for the Diagram

What

quantity (measure)
```
circle or elipse (regular, definite)
```
quality (sense)
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cloud (indefinite)
```

Relationships
- directly affects (more-->more;less-->less)
```
arrow
```
- inversely affects (more-->less;less-->more)
```
arrow with filled circle
```

Interventions

force directly
```
arrow with empty square
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force inversely
```
arrow with filled square
```

choice of forcing direction

arrow with diagonally lined square filled on bottom right

Hello everyone,

Here are my notes from the session:

You can go on forever trying to define and refine the problem statement. So define a problem statement and use it to establish the context of what you're trying to analyze. Once you've diagrammed the interactions, go back and modify the problem statement based on your new understanding of the situation.

These are the steps we went through to draw the diagram:

Draw the elements of the system (words in the picture)
Draw the relationships (green lines in the picture)
Draw the direction of the influence (the red arrows and circles on the lines)
Identify the feedback loops (the blue circular arrows)

As you are drawing the diagram, it helps to repeat the story -- starting from any element you like. Repeating the story helps you verify that your diagram makes sense. For example:

As the size of the factory increases, the cut rate increases, which increases the number of cut trees, which increases the number of thneads. (the story was about some trees that were used as raw material to make sweaters)

Once you've drawn the diagram, try to simplify as much as possible. Those are the crossed-out lines you see in the picture.

Seeing the system in this way helps you identify relationships you might not have considered otherwise. By seeing the relationships, you are in a better position to intervene in the system. We didn't get to that point in the session, but I spoke to MartineDevos who mentioned a cool simulation tool, called Vensim, that helps you actually see how your system behaves, and what effect your interventions have. BTW, for more on intervening in a system, see PreCedingsThree014.

Hope this helps! Take care, PhilippeBenitez 2003.11.12

Diagram of Effects

I didn't take a picture of the problem statement.

SteveSmith 2003.11.09

Some Participants

SteveSmith 2003.11.09

Updated: Wednesday, November 12, 2003