Eliot Lear wrote:
And, all of this can be automated.
How does my credit card company's billing system know which harris.com
to transmit my bill to? What unique attributes does it use to choose
between the two domains?
that's easy. Your credit card company has a previous relationship with
you and knows which harris.com to transmit to. Possibly, to the harris.com
defined at your root. In pretty much the same way, btw, that the credit card
company can disambiguate between you and any other Eliot Lear.