Agile Principles, Patterns, and Practices in C#

This principle deals with the disadvantages of "fat" interfaces. Classes whose interfaces are not cohesive have "fat" interfaces. In other words, the interfaces of the class can be broken up into groups of methods. Each group serves a different set of clients. Thus, some clients use one group of methods, and other clients use the other groups.

ISP acknowledges that there are objects that require noncohesive interfaces; however, it suggests that clients should not know about them as a single class. Instead, clients should know about abstract base classes that have cohesive interfaces.