Transforming cyclic schemas into trees

Abstract

A relational database schema can be thought of as a hypergraph whose nodes are attributes and whose edges are relations. One can partition the class of relational database schemas into tree schemas and cyclic schemas. A schema is a tree schema if there is a tree whose nodes are the schema's relations such that for each attribute, the subtree of nodes containing this attribute is connected. In [BFMMUY El], tree schemas are called acyclic hypergraphs while cyclic schemas are called cyclic hypergraphs.