One key abstraction

Riel's Heuristic #2.8

A class should represent one key abstraction of the domain model, no more and no less. A key abstraction is generally a noun in a requirements statement. If a key abstraction maps to more than one class, the designer may be representing each function of the abstraction as a class. If several key abstractions map to one class, the designer may be creating a centralized system and needs to split the class into several smaller classes.

See also

• Split large classes
• Riel's heuristics
• Single responsibility principle
• Separation of concerns