> The idea is to draw the line on class level, not on library level. And
> there I don't see it as a too difficult to to decide on whether a class is
> part of the framework or just a standalone tool class with no horizontal
> dependencies.

Well, it's slightly trickier than that: you're also deciding that the class 
will -never- get any horizontal dependencies. It may or may not be an issue 
depending on what happens with things like KGuiItem, KAction, etc.