magine you are going to build an airplane, entirely from scratch. Think about the
process you would follow. You very likely wouldn’t just head to a metal shop and
start welding. You’d have to draw up a blueprint for the airplane first. In fact, given
that you are building the airplane from scratch, you’d have to draw up not just one,
but many blueprints—one for each of the airplane’s many parts (the wheels, the
wings, the seats, the brakes, and so on). Each blueprint would describe a specific
part conceptually and correspond to an actual part in the physical incarnation of the
airplane. To build the airplane, you would manufacture each of the parts individually, and then assemble them according to a master blueprint. The interoperation of
the airplane’s assembled parts would produce the airplane’s behavior