Sequential Development vs. Agile Development

ABOUT THIS CHAPTER AND THE NEXT CHAPTER   “What’s Really Different About Agile?” and “Responding to the Challenges of Complexity and Uncertainty” describe foundational concepts for Agile software development that are referenced extensively throughout the rest of the course. If you jump ahead to later chapters, keep in mind that those discussions depend on ideas presented in these two chapters.

If you’d like to start with a big-picture overview, skip to the “Closing” chapter and read “Enjoy the Fruits of Your Labor” and “Summary of Key Principles.”

Most Agile courses with a lesson title like “What’s Really Different About Agile?” would immediately dive into historical descriptions of the 2001 Agile Manifesto and its related 20- year-old Agile Principles.

These documents served important and useful purposes 20 years ago, but Agile practices have continued to mature since then, and neither of these historic references accurately characterize the most valuable aspects of Agile today.

So, what is different about Agile today? The Agile movement historically contrasted itself with waterfall development. The claim was that waterfall development tried to do 100% of its planning up front, 100% of its requirements work up front, 100% of its design up front, and so on. This was an accurate characterization of literal “waterfall” development, but it described a mode of development that was never actually in widespread use. Various kinds of phased development were common.

True waterfall development existed mainly in early US Department of Defense projects, and that early crude implementation had already been superseded by more sophisticated lifecycles by the time the Agile Manifesto was written.

Different emphases between Sequential development and Agile development

The most meaningful contrast with Agile development today is Sequential development. Mischaracterizations aside, the contrasts are shown in the following table.