Thinking_in_Systems Flashcards
3 Parts of a System
- Elements
- Interconnections
- Function / Purpose
System
Interconnected set of elements that is coherently organized in a way that achieves something
Interconnections
Relationships that hold the elements together.
Can be physical flows or flows of information
If the interconnections change, the system may be greatly altered
“A system is more than the sum of its parts. It may exhibit adaptive, dynamic, goal-seeking, self-preserving, and something evolutionary behavior”
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Purpose
TODO
Best way to deduce the system’s purpose is to watch for a while to see how the systems behave
Deduced from behavior not from rhetoric or stated goals
An important function of almost every system is to ensure its own perpetuation
“Many of the interconnections in system operate through the flow of information. Information holds systems together and plays systems together and plays a great role in determining how they operate.”
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“The least obvious part of the system, its function or purpose, is often the most crucial determinant of the system’s behavior”
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Stock
The foundation of any system. Elements of the system that you can see, feel, count, or measure at any given time.
Change over time through the actions of a flow
The present memory of the history of changing flows within the system
Allows inflows and outflows to be independent of each other and temporarily out of balance with each other
Flows
The increase or decrease of the stock of a system
The filling and draining, births and deaths, purchases and sales, growth and decay, deposits and withdrawals, successes and failures.
“A stock is the memory of the history of changing flows within the system”
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Dynamics
The behavior over time of the stocks and flow of a system
Dynamic Equilibrium
When the flow of stock is such that the stock does not change. Inputs and outputs change at a constant rate with each other
“A stock can be increased by decreasing its outflow rate as well as by increasing its inflow rate. There’s more than one way to fill a bathtub!”
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“All models, whether mental models or mathematical models, are simplifications of the real world”
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“Stocks generally change slowly, even when the flows into or out of them change suddenly. Therefore, stocks act as delays or buffers or shock absorbers in systems”
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“Stocks allow inflows and outflows to be decoupled and to be independent and temporarily out of balance with each other”
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“System thinkers see the world as a collection of stocks along with the mechanisms for regulating the levels in the stocks by manipulating flows (feedback processes)”
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Feedback Loop
When changes in a stock affect the flows into or out of that same stock
Can cause stocks to maintain their level within a range or grow or decline. Flows into or out of the stock are adjusted because of changes in the size of the stock itself
“A feedback loop is a closed chain of causal connections from a stock, through a set of decisions or rules or physical laws or actions that are dependent on the level of the stock, and back again through a flow to change the stock”
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Balancing Feedback Loop
Equilibrating or goal-seeking structures in systems and are both sources of stability and sources of resistance to change
Reinforcing Feedback Loop
Self-enhancing, leading to exponential growth or to runaway collapses over time. They are found whenever a stock has the capacity to reinforce or reproduce itself. (Compound-interest account)
Think about this: If A causes B, is it possible that B also causes A?
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One-Stock Systems
TODO
A Stock with Two Competing Balancing Loops
(ex. Thermostat)
TODO
