In this paper, a series of design methods for relational databases based on generalization and aggregation sematics is set up. The relationship between a class and its subclass is considered as a scheme constraint. The concept of inheritance dependencies, which describes the multiple inheritance among schemes,is presented in the paper. It is shown that the inference rules for inheritance dependencies are sound and complete. Furthermore, a series of results about the closure of inheritance dependencies and the minimal set of inheritance dependencies, which are analogues to functional dependencies, is obtained. In order to describe the aggregation semalltics, the concept of aggregation dependencies is given. It is easy to implement these constraints under relational database management systems.
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