One-level deep inheritance can be great for abstracting common functionality, and multi-level inheritance sometimes makes sense in very large applications. Wha

One-level deep inheritance can be great for abstracting common functionality, and multi-level inheritance sometimes makes sense in very large applications. What you want to watch out for is multi-level inheritance with an inheritance hierarchy that parallels some hierarchy that is merely incidental to the code's functionality, like the page navigation hierarchy. I would say that having a multi-level inheritance hierarchy with greater than "constant" number of children per parent in one package is a code smell.