Software development as a system

What is a system?

A system is built from three things.

• Stocks are what you can see, count or measure at any moment. The backlog of user stories is a stock.

• Flows change a stock. Product managers adding stories to the backlog is a flow in; developers completing them is a flow out.

• Feedback loops are what the system tells you after an action.

Loops come in two kinds.

• A balancing loop says the outcome was bad and the behaviour has to change. Tests failing in CI is a balancing loop.

• A reinforcing loop says to keep going. QA sending nothing back to development is a reinforcing loop.

How do you know if you are looking at a system or a “bunch of stuff”?

• Can you identify parts?
• Do the parts affect each other?
• Do the parts together produce a result that none of them produces alone?