Single Responsibility Principle

External

• http://www.oodesign.com/single-responsibility-principle.html

Internal

• SOLID Principles
• [Designing Modular Systems#Cohesion|Designing Modular Systems]]

Overview

Robert C. Martin: Gather together those things that change for the same reason, and separate those things that change for different reasons.

Other formulation is: a class should have only a single reason to change.

The single responsibility principle is another way to define cohesion.