Improving semantic specification in a relational database

ABSTRACT

Standard semantics for the relational model considers domain values to be objects, which assume the roles indicated by the name of its associated attribute. Entities are related to each other to form tuples in a relation; attributes are also interrelated, but in this case the exact relationships have always been left implied or "intuitive." This paper introduces renaming rules, which are a way to formally specify these relationships. Properties of these rules are discussed, and a complete axiomatization is presented.Renaming rules allow meaningful equi-joins to be couched in terms of natural joins. They are intimately associated with the abstraction concept of generalization, and provide a natural semantics and theory for the relational algebraic operatiors select and union. These operators in turn use Smith's subcategory functional dependencies to achieve a better decomposition of a database scheme; to this end, a general normal form algorithm is presented.

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