Pattern	Purpose
Abstract Factory	many "platforms", one interface for creating a family of products
Builder	parse a complex representation, create one of several targets
Factory Method	dynamic (decoupled) creation through inheritance
Prototype	dynamic (decoupled) creation through delegation
Singleton	single instance enforcement, lazy initialization, global access
Adapter	impedance-match a legacy component to a new system
Bridge	decouple interface from implementation; move beyond encapsulation to insulation
Composite	recursive composition by coupling the aggregate class to a common abstraction
Decorator	recursive wrappering that supports client-specified incremental embellishment
Facade	simple wrapper (or surrogate) to a complicated subsystem
Flyweight	use sharing to optimize the use of lots of "little" objects
Proxy	use an extra level of indirection to support distributed, controlled, or intelligent access
Chain of Respon	OO linked list; launch-and-leave requests with a simple processing pipeline
Command	OO callback; promote a method invocation on an object to "full object status"
Interpreter	map: domain => language => grammar => hierarchical OO design
Iterator	an interface that supports the decoupling of algorithms and data structures
Mediator	decouple many peers by promoting many-to-many relationships to "full object status"
Memento	OO undo/rollback; externalize an object's state to an opaque object
Observer	decouple independent sender (model) from dependent receivers (views)
State	OO finite state machine; state inheritance hierarchy, current state wrapper
Strategy	legoware algorithm; publish interface in a base class, bury impl in derived classes
Template Method	common algorithm and placeholders in base class, variable steps in derived classes
Visitor	open for extension, closed for modification; add methods w/o changing existing classes