What is the Abstract Interface Pattern?

The abstract interface pattern combines the benefits of interfaces (contract for behavior) and abstract skeletal implementations (much like the Strategy design pattern from Gamma et al). In a layered architecture an abstract interface is defined for each component in a layer that is called by components in a higher level. The higher layers access the lower-level components through the abstract interfaces instead of calling the components directly. This allows for the changing of lower level components without affecting the higher level components.