Depends on what kind of user experience you're trying to program. For instance, the post office has multiple levels of precision -- state, city, street, etc., a

Depends on what kind of user experience you're trying to program. For instance, the post office has multiple levels of precision -- state, city, street, etc., and managed to deliver the mail prior to the computer age. On the other hand, limitations of conventional floating point are imaginable, in which case you choose a different kind of numbering system. As it stands right now the typically cited value for the distance to Alpha Centauri doesn't take the position of the earth relative to the sun into account. We live with this imprecision. And in the post office example, a conventional address would be problematic because a person might move during the 8 year round trip between the stars.