Royce's "Waterfall" diagram looks nice as a linear flow from idea to execution. Royce himself even intended that it not be overly linear... but the degree of feedback and interconnection between the different states to deal with reality is SO high that the linear model in theory ends up a tangled mess in reality.

1. “ Managing the Development of Large Software Systems” (Dr. Winston Royce, Lockheed/NASA, 1970) 09/26/10 SYSTEM REQUIREMENTS SOFTWARE REQUIREMENTS ANALYSIS PROGRAM DESIGN CODING TESTING OPERATIONS

2. “ Managing the Development of Large Software Systems” (Dr. Winston Royce, Lockheed/NASA, 1970) 09/26/10 SYSTEM REQUIREMENTS SOFTWARE REQUIREMENTS ANALYSIS PROGRAM DESIGN CODING TESTING OPERATIONS

3. “ Managing the Development of Large Software Systems” (Dr. Winston Royce, Lockheed/NASA, 1970) 09/26/10 SYSTEM REQUIREMENTS SOFTWARE REQUIREMENTS ANALYSIS PROGRAM DESIGN CODING TESTING OPERATIONS TESTING