The devil's in the details and each situation is different. One has to know the domain well to make decent guesses about likely future change patterns. Making c

The devil's in the details and each situation is different. One has to know the domain well to make decent guesses about likely future change patterns. Making code future-friendly is hard and requires experience both in coding and the domain. Let's look at UI's. Should "buttons" and "hyperlinks" be considered different "types" of things? Or should we blur the distinction to be flexible? In this view, a button is a style applied to a hyperlink rather than a distinct "kind" of thing. Once you pre-type them into distinct things, it's hard to merge them: the code base hard-wires a clear distinction and too many things rely on a type-centric arrangement. A more flexible approach is to take the view that things, perhaps ANY thing, wants the ability to "act like" a hyperlink and/or button. Linking is then viewed as an optional feature, not part of some base "type". Same with drop-downs versus combo-boxes versus text boxes: we can model these via feature smorgasbords instead of sub-types and probably get a more flexible framework in the process that may also be reusable in other widgets. But the flip-side is that such flexibility can confuse newbies. Hard-wired hierarchies are quicker to learn, and test.