As discussed earlier viral marketing is a form of word of mouth marketing which is carried out using online means. (Click here for the Introduction to Viral Marketing) Viral marketing is practiced by business organization who are engaged in e-commerce and many organizations have become a success stories by using viral marketing strategies. Hotmail.com is a the best example that can be quoted. Hotmail provided free sign up for users who were interested in obtaining an email account and they were [...]

Intent Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically. Applicability Use Observer pattern when An abstraction has two aspects, one dependent on the other. Encapsulating these aspects in separate objects let you vary and reuse them independently. A change to one object requires changing others, and you don’t know how many objects need to be changed. An object should be able to [...]

Viral marketing is a form of word of mouth marketing where it uses the online means to promote a product. In other words, viral marketing uses internet to spread the message of product like how a virus is spread among computers which are networked. As an example, if an email message is sent passed to few audience from the target market they may forward it to others who have similar interest and the forward chain will keep [...]

Motivation As a class developer, you will ordinarily provide class constructors to let users of your class instantiate it. However, a client that needs an object does not or should not know which of several possible classes to instantiate.   Intent Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.   Applicability Use Factory Method pattern when • In order [...]

Intent Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to sub-classing for extending functionality. [GoF, p175] Client-specified embellishment of a core object recursively wrapping it.   Diagram   Rules of thumb Adapter provides a different interface to its subject. Proxy provides the same interface. but the decorator provides an enhanced interface. [Gof, p216] Adopter changes an object’s interface, Decorator enhances an objects responsibilities, Decorator is thus more transparent to the client. [...]

Motivation There are situations where the classes differ only by their behaviour, and on such situations it is advisable to isolate the algorithms into separate classes in order to have the ability to select different algorithms at the runtime depending on the user needs/client inputs.   Intent “Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it.” [Gamma, p315] Capture the [...]