Decomposition by Pivoting and Path Cardinality Constraints
In the relational data model, the problem of data redundancy has been successfully tackled via decomposition. In advanced data models, decomposition by pivoting provides a similar concept. Pivoting has been introduced by Biskup et al. , and used for decomposing relationship types according to a unary nonkey functional dependency. Our objective is to study pivoting in the presence of cardinality constraints which are commonly used in semantic data models. In order to ensure the equivalence of the given schema and its image under pivoting, the original application-dependent constraints have to be preserved. We discuss this problem for sets of participation and co- occurrence constraints. In particular, we prove the necessity of path cardinality constraints, and give an appropriate foundation for this concept.
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