A uniform approach toward handling atomic and structured information in the nested relational database model

TLDR: An algebra is proposed that does allow us to simplify relations by disregarding the internal structure of a certain class of information, based on a careful manipulation of attribute names.

Abstract: The algebras and query languages for nested relations defined thus far do not allow us to “flatten” a relation scheme by disregarding the internal representation of data. In real life, however, the degree in which the structure of certain information, such as addresses, phone numbers, etc., is taken into account depends on the particular application and may even vary in time. Therefore, an algebra is proposed that does allow us to simplify relations by disregarding the internal structure of a certain class of information. This algebra is based on a careful manipulation of attribute names. Furthermore, the key operator in this algebra, called “copying,” allows us to deal with various other common queries in a very uniform manner, provided these queries are interpreted as operations on classes of semantically equivalent relations rather than individual relations. Finally, it is shown that the proposed algebra is complete in the sense of Bancilhon and Paredaens.