 It is clear that a circle cannot satisfy the invariants required of it while its base ellipse methods allow mutation of parameters.However, the possibility exists that when a circle cannot meet the circle invariants, its type can be updated so that it becomes an ellipse.If a circle which has become a "de facto" ellipse doesn't change type, then its type is a piece of information which is now out of date, reflecting the history of the object (how it was once constructed) and not its present reality (what it has since mutated into).