Challenge Your Assumptions If you think that the object you are designing must be mutated by its behavior, ask yourself why that is necessary. Would it be possible instead to use replacement when the Value must change? Using this approach where possible is designing toward simplification. Sometimes it makes no sense for an object to be immutable. That’s perfectly fine, and it indicates that the object should be modeled as an Entity. If your analysis leads you to that conclusion, refer to Entities (5).
