Application of SQL/N to the attribute-relation associations implicit in functional dependencies

Abstract

SQL/N is an expressive nonprocedural data base language that is upward compatible with SQL. Its expressive power is derived from both the use of natural quantifiers and the quantification of subsets of relations, in particular the subsets that are the groups of related tuples that occur in associations between relations. We show that SQL/N is also very expressive in specifying requests involving attribute-relation associations, and that attribute-relation associations are implicit in functional dependencies. We show that an attribute-relation association may be derived from the association between an algebraic projection relation and the relation on which the projection operation is performed. Two common cases of attribute-relation associations are investigated: first the case of an association restricted to a single relation, and second a more general attribute-relation association where an attribute from one relation is associated with a second relation.