Design by example: An application of Armstrong relations

摘要

Example relations, and especially Armstrong relations, can be used as user friendly representations of dependency sets. In this paper we analyze the use of Armstrong relations in database design with functional dependencies, and show how they and the usual representation of dependencies can be used together. Special attention is given to the size of Armstrong relations. We derive new bounds for the size of minimal Armstrong relations for normalized schemes. Specifically, any relation scheme in Boyce-Codd Normal Form has an Armstrong relation whose size is roughly the product of the lenghts of the keys for the scheme. New algorithms are also given for generating Armstrong relations and for inferring the functional dependencies holding in a relation.