Half-adder can be used for counting numbers - bunch of adders with the combined logic are realizing the adding of binary numbers. Also half-adder logic similar to XOR element. In Berkley's publication is using AND,NOT,OR elements.
Counting numbers, in parallel by counting digits, from the right to the left.
It is a "global" scheme, because possible to count whole numbers. For adding length of number we can add new repeatable patterns of half-adders and OR.