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On interpretations of relational languages and solutions to the implied constraint problem

The interconnection between conceptual and external levels of a relational database is made precise in terms of the notion of “interpretation” between first-order languages. This is then used to obtain a methodology for discovering constraints at the external level that are “implied” by constraints at the conceptual level and by conceptual-to-external mappings. It is also seen that these concepts are important in other database issues, namely, automatic program conversion, database design, and compile-time error checking of embedded database languages. Although this the deals exclusively with the relational approach, it also discusses how these ideas can be extended to hierarchical and network databases.