None User Services There are eight structural design patterns in the Design Patterns book: Adapter, Bridge, Composite, Decorator, Facade, Flyweight, and Proxy. Three have proven to be useful in the logical design: Adapter, Composite, and Facade. Unsurprisingly, the Facade pattern is the cornerstone for the Facade layer. As discussed in detail in Module 5, “The Facade Layer,” the Facade pattern provides for a common secure interface to the internals of an application. This interface allows user services to become impervious to changes in the internal structure of applications.