Imagine a friend asks you to build a house. You could just grab a hammer and start nailing boards together, but you would probably sketch a floor plan first — or you might build a small model to see if the layout works before committing. Building an information system is the same. There are many ways to get from a business need to a working piece of software, and the method you choose shapes cost, speed, risk, and how well the final system fits. This chapter compares the major approaches, from careful step-by-step blueprints to quick prototypes that evolve with constant feedback.