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Introduction to Systems Thinking:
System Structures and Behaviour
Sydney Limited WIP Society
Jason Yip
j.c.yip@computer.or...
Select a problem as a working
example. It should be somewhat
complicated, and not too simple.
What is a system?
A system is a set of things
interconnected in such a way that
they produce their own pattern of
behaviour over time
A system is more than the sum of its
parts
http://mennodiscuss.com/viewtopic.php?f=6&t=16392#p456262
Systems consists of three things
1. Elements
2. Interconnections
3. Function (non-human system) or Purpose
(human system)
Examples of systems
● Digestive system
● Sports team
● School
● City
● Factory
● Corporation
● National Economy
● Animal
●...
https://flic.kr/p/97JeYs
“Bicycle system”
“Frog system”
https://flic.kr/p/mKKug
Systems mostly cause their own
behaviour; outside events unleash
that behaviour
Do politicians cause recessions and
booms? Or is it inherent to market
economies?
Do competitors cause companies to
lose market share? Or do their own
policies create losses that
competitors exploit?
“Every system is perfectly designed
to achieve the results it gets.”
Dr. Don Berwick
Describe your situation as a system
● What are the elements?
● What are the interconnections between the
elements?
● What ...
Stocks and Flows
Stocks are the elements you can see,
feel, count, or measure at any given
time
Examples of Stocks
● Water in a bathtub
● A population
● Books in a book store
● Wood in a tree
● Money in a bank
Stocks change over time via Flows
● Work flow
● Information flow
● Both inflow and outflow
http://lssacademy.com/2008/02/24/lets-create-a-current-state-value-stream-map/
Information Flow
Work Flow
Stocks
https://flic.kr/p/9az8q1
Inflow
Outflow
Information flow
Stock
Stocks provide a memory of flows
Stocks act as “shock absorbers”
Stocks introduce delay.
It takes time for flows to affect
stocks.
Delays decouple inflow and outflow
Examples of stocks decoupling flows
● Gasoline storage tanks
● Wood in a forest
● Water reservoir
“Stocks are pretty much queues”
Me
Let’s try describing a typical Agile
team using stocks and flows
How might stocks and flows change
how you describe your situation?
Feedback loops
Systems run themselves via
feedback loops
Balancing feedback loops
● Thermostat
● Guided missile
● Iterative, incremental software development
A stock with two competing
balancing loops
How feedback fails
● Late, lost, unclear, incomplete, hard to
interpret information
● Weak, delayed, resource-constrained,...
Two competing balancing loops with
delays
The problem with forecast-driven
supply chains
A delay in a balancing feedback loop
makes a system likely to oscillate
Aside: This is generally solved by
using kanban
Reinforcing feedback loops
● Market collapse: uncertainty -> remove
money -> more uncertainty
● Compound interest
● Death ...
A stock with one reinforcing loop
and one balancing loop
If A causes B, is it possible that B
also causes A?
How might feedback loops change
how you describe your situation?
Dealing with systems
Systems consists of three things
1. Elements
2. Interconnections
3. Function (non-human system) or Purpose
(human system)
Changing elements usually has the
least effect; changing
interconnections or purpose is
usually more dramatic
Examples
● Change all members of a sports team vs
change rules of the game or the definition of
winning
● Change people in...
Focus more on interconnections and
interactions than elements
● Interaction flow / sequence over class
structure
● Work fl...
System interactions operate through
information flow
Address incongruent purposes
System purposes do not necessarily match the
intention of the designers or actors within it
How might you intervene in your
situation to improve the system?
Introduction to Systems Thinking: System Structures and Behaviour
Introduction to Systems Thinking: System Structures and Behaviour
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Introduction to Systems Thinking: System Structures and Behaviour

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Presentation for the Sydney Limited WIP Society

An introduction to Systems Thinking for people who I assume are familiar with designing, building IT systems and/or the mess of large organisations

Targeting beginners OR a review of fundamentals for non-beginners

Transcript of "Introduction to Systems Thinking: System Structures and Behaviour"

  1. 1. Introduction to Systems Thinking: System Structures and Behaviour Sydney Limited WIP Society Jason Yip j.c.yip@computer.org http://jchyip.blogspot.com @jchyip
  2. 2. Select a problem as a working example. It should be somewhat complicated, and not too simple.
  3. 3. What is a system?
  4. 4. A system is a set of things interconnected in such a way that they produce their own pattern of behaviour over time
  5. 5. A system is more than the sum of its parts
  6. 6. http://mennodiscuss.com/viewtopic.php?f=6&t=16392#p456262
  7. 7. Systems consists of three things 1. Elements 2. Interconnections 3. Function (non-human system) or Purpose (human system)
  8. 8. Examples of systems ● Digestive system ● Sports team ● School ● City ● Factory ● Corporation ● National Economy ● Animal ● Tree ● Forest ● Earth ● Solar system ● Galaxy ● IT system
  9. 9. https://flic.kr/p/97JeYs “Bicycle system”
  10. 10. “Frog system” https://flic.kr/p/mKKug
  11. 11. Systems mostly cause their own behaviour; outside events unleash that behaviour
  12. 12. Do politicians cause recessions and booms? Or is it inherent to market economies?
  13. 13. Do competitors cause companies to lose market share? Or do their own policies create losses that competitors exploit?
  14. 14. “Every system is perfectly designed to achieve the results it gets.” Dr. Don Berwick
  15. 15. Describe your situation as a system ● What are the elements? ● What are the interconnections between the elements? ● What is the purpose of the system? Intended vs actual based on behaviour?
  16. 16. Stocks and Flows
  17. 17. Stocks are the elements you can see, feel, count, or measure at any given time
  18. 18. Examples of Stocks ● Water in a bathtub ● A population ● Books in a book store ● Wood in a tree ● Money in a bank
  19. 19. Stocks change over time via Flows ● Work flow ● Information flow ● Both inflow and outflow
  20. 20. http://lssacademy.com/2008/02/24/lets-create-a-current-state-value-stream-map/ Information Flow Work Flow Stocks
  21. 21. https://flic.kr/p/9az8q1 Inflow Outflow Information flow Stock
  22. 22. Stocks provide a memory of flows
  23. 23. Stocks act as “shock absorbers”
  24. 24. Stocks introduce delay. It takes time for flows to affect stocks.
  25. 25. Delays decouple inflow and outflow
  26. 26. Examples of stocks decoupling flows ● Gasoline storage tanks ● Wood in a forest ● Water reservoir
  27. 27. “Stocks are pretty much queues” Me
  28. 28. Let’s try describing a typical Agile team using stocks and flows
  29. 29. How might stocks and flows change how you describe your situation?
  30. 30. Feedback loops
  31. 31. Systems run themselves via feedback loops
  32. 32. Balancing feedback loops ● Thermostat ● Guided missile ● Iterative, incremental software development
  33. 33. A stock with two competing balancing loops
  34. 34. How feedback fails ● Late, lost, unclear, incomplete, hard to interpret information ● Weak, delayed, resource-constrained, ineffective response
  35. 35. Two competing balancing loops with delays
  36. 36. The problem with forecast-driven supply chains
  37. 37. A delay in a balancing feedback loop makes a system likely to oscillate
  38. 38. Aside: This is generally solved by using kanban
  39. 39. Reinforcing feedback loops ● Market collapse: uncertainty -> remove money -> more uncertainty ● Compound interest ● Death march: Too much to do -> work harder -> more bugs -> work even harder
  40. 40. A stock with one reinforcing loop and one balancing loop
  41. 41. If A causes B, is it possible that B also causes A?
  42. 42. How might feedback loops change how you describe your situation?
  43. 43. Dealing with systems
  44. 44. Systems consists of three things 1. Elements 2. Interconnections 3. Function (non-human system) or Purpose (human system)
  45. 45. Changing elements usually has the least effect; changing interconnections or purpose is usually more dramatic
  46. 46. Examples ● Change all members of a sports team vs change rules of the game or the definition of winning ● Change people in the organisation vs change the way of working or the definition of organisational success
  47. 47. Focus more on interconnections and interactions than elements ● Interaction flow / sequence over class structure ● Work flow / value stream over org structure
  48. 48. System interactions operate through information flow
  49. 49. Address incongruent purposes System purposes do not necessarily match the intention of the designers or actors within it
  50. 50. How might you intervene in your situation to improve the system?
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