The Antenna Design Framework -ElectroMagnetic Satellite is an antenna design system offering a wide palette of modeling tools aimed at covering engineering needs from the early feasibility studies to the last performance-verification stages of flight hardware. A few key ideas have been central to its development, focusing on the overall engineering process rather than on individual modeling steps. This has led to a modeling architecture that offers a very high degree of modularity, scalability, and flexibility. Some practical examples are used in the discussion to illustrate these points.