A systematic approach to relational database theory

In an attempt to eliminate motivational inconsistencies, we propose a new approach to relational database theory. Basically, a database schema is treated as a relational view defined over certain atomic, selfexplainable relations, constituting what we call a conceptual schema. In this new framework, we revisit some basic notions of the relational database theory, such as dependencies and schema equivalence. We point out a fundamental difference between functional dependencies, which we treat as constraints over the conceptual schema, and multivalued and join dependencies, which we treat as constraints over the database schema, and which are simply consequences of the way database relations are constructed from conceptual relations. The separation of the database schema from the conceptual schema makes it possible to give a clear definition of a semantics of a database state. It also provides a natural framework to consider equivalence of database schemata.