A model is a simplified representation of a thing or phenomenon that intentionally emphasi‐ zes certain aspects while ignoring others. Abstraction with a specific use in mind.

—Rebecca Wirfs-Brock

A model is not a copy of the real world but a human construct that helps us make sense of real-world systems.

A canonical example of a model is a map. Any map is a model, including navigation maps, terrain maps, world maps, subway maps, and others, as shown in Figure 2-3.

Figure 2-3. Different types of maps displaying different models of the earth: roads, time zones, nautical navigation, terrain, aeronautical navigation, and subway routes.

None of these maps represents all the details of our planet. Instead, each map con‐ tains just enough data to support its particular purpose: the problem it is supposed to solve.