Behavioral patterns List

Pattern Name	Purpose/Description
Blackboard	Artificial intelligence pattern for combining disparate sources of data
Chain of responsibility	Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request.  Chain the receiving objects and pass the request along the chain until an object handles it.
Command	Encapsulate a request as an object, thereby allowing for the parameterization of clients with different requests, and the queuing or logging of requests.  It also allows for the support of undo-able operations.
Interpreter	Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.
Iterator	Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
Mediator	Define an object that encapsulates how a set of objects interact.  Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and  it allows their interaction to vary independently.
Memento	Without violating encapsulation, capture and externalize an object's internal state  allowing the object to be restored to this state later.
Null object	Avoid null references by providing a default object.
Observer or Publish/subscribe	Define a one-to-many dependency between objects where a state change in one object results in all  its dependents being notified and updated automatically.
Servant	Define common functionality for a group of classes.
Specification	Recombinable business logic in a Boolean fashion.
State	Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.
Strategy	Define a family of algorithms, encapsulate each one, and make them interchangeable.  Strategy lets the algorithm vary independently from clients that use it.
Template method	Define the skeleton of an algorithm in an operation, deferring some steps to subclasses.  Template method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.
Visitor	Represent an operation to be performed on the elements of an object structure. Visitor lets a new operation be defined without changing the classes of the elements on which it operates.