1. An arrangement comprising: a processor; a plurality of satellite databases communicating with said processor, each storing data; and a materialized database, under control of said processor, that stores a union of the data stored in all of said satellite databases, where said processor includes a queue and a controller that, through updates sent from said satellite databases to said processor, and updates sent from said controller to said satellite databases and to said materialized database, maintains consistency among said satellite databases and said materialized database.