On: Inheritance Often Doesn't Make Sense

[PKop]

I don't think the "that can change" characteristic is important here.

You can declare that "for all values of width and height, w does not have to equal h" to be valid. Mutability is irrelevant.

[kqr → PKop]

But a rectangle as traditionally defined can have equal dimensions. Consider the rectangle whose width slowly grows to be longer than the height. Surely it does not skip a value because it happens to equal the height?

[PKop → kqr]

"does not have to be equal" != "can't be equal".

The set of all possible rectangles have w and h that can be different (or the same) values.