Epilogue: The Value of Sequence Diagrams

You may ask yourself: Why should I use sequence diagrams? Can't you just immediately build a state machine or write code for your system? Of course, you could. But then again, would you build a house before drawing it?

Depending on the project, sequence diagrams may be mandatory and part of a formal specification, or they may just be something that you scribble on a whiteboard or a piece of paper. The actual value of writing down interactions by sequence diagrams comes then from the following:

  1. They make you think about interactions.

  2. They enable you to explain interactions to others, discuss interactions in team.

  3. They let you find trouble spots.

  4. You can resolve intricate situations.

So, the value of sequence diagrams depends on how they are used in the development process, and how they effectively improve the system design. In some cases, just the fact that you sit down and sketch some interactions changes your view on the system, leads to good design choices and prevents errors in the first place. A single relevant sequence diagram, sketched on a paper that uncovers problems in your system design early, can save millions in whatever currency.

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