The revenge of the JD
David Maier, Jeffrey David Ullman, Moshe Y. Vardi · 1983
Manifestations of the "universal relation assumption" can be seen either as definitions of a one-relation user view of data, or as algorithms for answering queries about arbitrary sets of attributes. In this paper we explore equivalences between these two points of view. We show that if the user's view is the representative instance, then our ability to answer queries about the universal relation, by applying relational algebra to the actual database, is equivalent to a "boundedness" condition on the dependencies of the database scheme. Further, whenever this condition holds, there is a finite union of lossless tableau mappings that produces the desired relation.