Understanding the Circle-Ellipse Problem in Object-Oriented Programming: Subclassing Pitfalls and Solutions
The Circle-Ellipse Problem is a modeling failure in object-oriented programming that is the result of a number of misunderstandings and incorrect assumptions about the modeling domain and about subtyping relationships. Applying accepted software design principles exposes several problems in the circle-ellipse problem and indicates how the problem can be avoided altogether. The Circle is-a Ellipse