A new 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 the nested normal form. Given a set of attributes U , and a set of multivalued dependencies (MVDs) M over these attributes, we present an algorithm to obtain a nested normal form decomposition of U with respect to M . Such a decomposition has several desirable properties, such as explicitly representing a set of full and embedded MVDs implied by M , and being a faithful and nonredundant representation of U . Moreover, if the given set of MVDs is conflict-free, then the nested normal form decomposition is also dependency-preserving. Finally, we show that if M is conflict-free, then the set of root-to-leaf paths of scheme trees in nested normal form decomposition is precisely the unique 4NF decomposition [9, 16] of U with respect to M .