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Object-Role Modeling Workbook: Data Modeling Exercises using ORM and NORMA by Terry Halpin

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5    Transforming and Optimizing Schemas

This chapter discusses some of the main ways of transforming ORM schemas into alternative but equivalent schemas, and provides guidelines for choosing such transformations in order to optimize or improve the efficiency of the relational schema generated from the ORM schema via the Rmap procedure. It also includes exercises to consolidate the ideas discussed. Exercise answers are in the back of the book.

5.1    Conceptual Schema Transformations

Basically, two schemas are semantically equivalent if and only if each UoD state or transition that can be modeled in one schema can also be modeled in the other. Intuitively, most people would regard the ORM schemas in Figure 5.1 to be equivalent in this way. Given ...

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