In one sense, the process of inheritance is a form of categorization.
A TextWindow is a type of Window, so class TextWindow inherits from
class Window.
But in the real world, most objects can be categorized in a variety of
ways. The author of the textbook is
- North American
- Male
- Professor
- Parent
None of these are proper subsets of the other, and we cannot
make a single rooted inheritance hierarchy out of them.