Avoiding Over and Under Design

The question of how much design to do up-front on a project is an engaging one. Too much design often results in overkill, complexity, and wasted work. Too little design results in insufficient system structures that require rework, additional complexity, and wasted effort. How can we know what the right balance is? Alan Shalloway shows how to use the advice from Design Patterns coupled with the attitude of not building what you don't need from Agile. The trick is in discovering what you don't know, how it may affect you, and then how to isolate these risks in your code in a simple manner. Alan describes the essence of emergent design–that is, starting with a simple design and letting it evolve as the requirements evolve. He also demonstrates how to refactor to better designs and how this is different from refactoring bad code.