We introduce and study the concept of domain independence to characterize the class of reasonable databases. A domain independent database is one for which the set of correct answers to an atomic query is independent of the domains of variables in the database statements. In particular, we prove that every “allowed” stratified database is domain independent and that every domain independent stratified database has an equivalent allowed database. We contrast these results with those of an earlier paper in which a different definition of a correct answer was used.
