At a press conference in 2003, Donald Rumsfeld, Secretary of Defense in the Bush Administration, made the following statement:
Reports that say something hasn't happened are always interesting to me because, as we know, there are known knowns, there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know.
No doubt unknowingly, Mr. Rumsfeld has provided us with a superb introduction to the topic of nulls and zero-length strings.
Thus far, we've been dealing with values that are “something”—Helen, coffee, 378, 10/11/97, and so on. But what about ...