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Diagram: interaction of fundamental activities

publish date: 2026/05/29 21:38:7.490034 UTC

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The following simple diagram shows the interaction between the four fundamental activities.

What key idea does this diagram convey?

Evolution happens before any other activity

Only specification and development are important in practice

The four activities are distinct but linked by feedback and iteration

The four activities must be performed exactly once in strict sequence

The four activities are distinct but linked by feedback and iteration

The diagram emphasizes that although the activities are conceptually distinct, they are connected and often revisited during the process.

Software Engineering, Ian Sommerville, 9th edition