A NORMAL FORM FOR NESTED RELATIONS

Abstract

We consider nested relations whose schemes are structured as trees, called scheme trees, and introduce a normal form for such relations, called nested normal form. Given a universal scheme U, and a set of multivalued dependencies (MVD's) M, we present an algorithm to obtain a nested normal form decomposition of U w.r.t. M. Such a decomposition has several desirable properties, such as explicitly representing a set of full and embedded MVD's implied by M, and being a faithful and nonredundant representation of U. Moreover, if M is conflict free, then the nested normal form decomposition is also dependency preserving. Finally, we show that if M is conflict free, then the unique 4NF decomposition [Fa, L2 ] (which is also in SFNF [BK2]), of U is precisely the set of roo1>to-leaf paths of scheme trees in nested normal form decomposition of U w.r.t. M.