For questions about the Interface Segregation Principle (ISP) in object-oriented design, one of the SOLID principles enumerated by Robert C. Martin. It states that "clients should not be forced to depend upon interfaces that they do not use."
Robert Martin introduced the Interface Segregation Principle in 1996. It seeks to avoid coupling between different clients of an interface.
When clients are forced to depend upon interfaces that they don’t use, then those clients are subject to changes to those interfaces. This results in an inadvertent coupling between all the clients. Said another way, when a client depends upon a class that contains interfaces that the client does not use, but that other clients do use, then that client will be affected by the changes that those other clients force upon the class. We would like to avoid such couplings where possible, and so we want to separate the interfaces where possible.
Martin proposed the adapter pattern as a solution to achieve interface segregation.
By making use of the ADAPTER pattern, either through delegation (object form) or multiple inheritance (class form), fat interfaces can be segregated into abstract base classes that break the unwanted coupling between clients.
Martin later included the ISP as the fourth of his solid-principles.
See the ISP article under Principles of OOD.
