Systems

Question 1

System Representations

Answer 1

a) Networks
b) rich pictures/mind maps
c) hierachy trees
d) entity-process diagram
e) logic flow diagrams
f) cross-functional diagrams
g) entailment trees
h) influence (causal-loop) diagrams
i) stock/flow diagrams

Question 2

Developing a system representation

Answer 2

• think about the purpose
• list the components
• list the important process or links between components
• choose a representation
• draft the system representation
• check against the ‘Healthy system’ criteria

Question 3

Healthy systems representations have:

Answer 3

a) balance
b) completeness
c) cohesion
d) discrimination
e) consistency

Question 4

positive link

Answer 4

• means they go up and down together

Question 5

negative link

Answer 5

• means when one goes up, the other goes down

Question 6

positive feedback loop

Answer 6

• when product of all links is >0

- snowballs to a limit

Question 7

negative feedback loop

Answer 7

• when product of all links is < 0

- finds a balance

Question 8

steps in design

Answer 8

1. think of the processes that interact
2. figure out the key variables involved in multiple processes
3. start with a simple or fundamental process with a simple explanation
4. expand by thinking about when this process does or does not dominate and how other processes interact to give other solutions
5. test logic of your diagram
   - does this describe every way that ‘x’ could change?
   - are there redundant parts?

Question 9

Pitfalls to avoid

Answer 9

• no loops, dead-ends
• poor names for variables
• too many links, variables
• two-step loops
• capture causation not correlation