Interfaces

Defining interfaces and creating components that implement the interfaces can increase flexibility. Components can be replaced and different implementations combined. It can give a reassuring feeling that a design can evolve over time.

Note that part of the value of an interface is that it provides "information hiding." This was a radical concept in the 1960's. It allows the implementation details of a component to be shielded from other code. This prevents unwanted dependencies from other components from preventing updates.

In real life, components are often replaced and combined without an informed decision. The book Fate is the Hunter (1961) by Ernest K. Gann describes a negligent lack of caution in replacing critical components in passenger aircraft, for example. Also, some people insist on extremely high granular components. The hope is that almost anything can be replaced with little effort. This can district and divide teams.