http://www.cnblogs.com/shanyou/archive/2009/09/21/1570716.html
SOLID is object-oriented design and programming (OOD & OOP) in several important coding principles (Programming Priciple) acronym.
| SICKLE | The Single Responsibility Principle | Single Responsibility Principle |
| OCP | The Open Closed Principle | Open Closed Principle |
| LSP | The Liskov Substitution Principle | Richter substitution principle |
| DIP | The Dependency Inversion Principle | Dependency Inversion Principle |
| ISP | The Interface Segregation Principle | The principle of separation Interface |
Single Responsibility Principle:
When the need to modify a class when there is one and only one reason (THERE SHOULD NEVER BE MORE THAN ONE REASON FOR A CLASS TO CHANGE). In other words, to make a class only one type of liability, when the class needs to assume responsibility for other types of time, we need to break this class.
Open Closed Principle
Software entities should be scalable, and can not be modified. That is, the expansion is open and closed for modification. This principle is a lot of object-oriented programming principles in the most abstract, the most difficult one to understand.
Alternatively Richter principle
when a child instance of the class should be able to replace any instance of its superclass, only with the relationship between them is-A Dependency Inversion Principle 1. The layer module should not depend on low-level modules, to be dependent on both abstract 2. abstract should not depend on the details, the details should depend on abstractions 
Interface Segregation principle
can not force users to rely on those interfaces that they do not use. In other words, a plurality of dedicated interfaces than using a single interface to the total overall better.
Several of these principles are very basic and important object-oriented design principles. It is because of these fundamental principles, understanding, mastered these principles require a lot of experience and accumulated knowledge. The above picture is well commented this several principles.