Dependency Inversion Principle

A specific form of decoupling software modules. When following this principle, the conventional dependency relationships established from high-level policy-setting modules to low-level dependency modules are reversed, thus rendering high-level modules independent of the low-level module implementation details. The principle states 1) that high-level modules should not depend on low-level modules, but that both should depend on abstractions (e.g., interfaces), and 2) that abstractions should not depend on details, but that details (concrete implementations) should depend on abstractions. ← Wikipedia