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This monograph provides a rigorous foundation for handling business and engineering data based on unnormalized relations. It can be used by practitioners, researchers, and students for self study or as a textbook. Both theoretical and practical aspects are discussed in this volume. In the relational data model, data objects are modeled as flat tables under a certain constraint. This constraint excludes nests of columns and/or rows from the relational data model. Therefore, extensions of the original relational data model have been proposed. In the nested table data model discussed here data are modeled as a collection of tables. This model is presented to provide a theoretical basis for modeling practical data in nested table forms. It is then applied to the design and implementation of a database workbench featuring an interactive manipulation of form-based documents. Nested tables are also used for application system generation. The book includes a useful overview of significant works relating to this important area of database research.