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Diagram: waterfall with feedback

publish date: 2026/05/28 22:08:35.084971 UTC

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The following diagram shows a more realistic waterfall with feedback loops.

What do the curved arrows in this diagram represent?

User navigation paths in a user interface.

Feedback from later phases to earlier phases when problems are discovered.

Random jumps between phases with no rationale.

Data flow between unrelated systems.

Feedback from later phases to earlier phases when problems are discovered.

The arrows show that issues found in later phases (e.g., testing) may require revisiting earlier phases (e.g., design or requirements).

Software Engineering, Ian Sommerville, 9th edition