The Nested Universal Relation Database Model DJVU

The Nested Universal Relation Database Model By Mark Levene
Publisher: Spr..ing..er 1992 | 187 Pages | ISBN: 3540554939 , 0387554939 | DJVU | 2 MB

This monograph describes a method of data modelling whose basic aim is to make databases easier to use by providing them with logical data independence. To achieve this, the nested UR (universal relation) model is defined by extending the classical UR model to nested relations. Nested relations generalize flat relations and allow hierarchically structured objects to be modelled directly, whereas the classical UR model allows the user to view the database as if it were composed of a single flat relation. The author presents a comprehensive formalisation of the nested relational model, which incorporated null values into the model. Functional data dependencies and the classical notion of lossless decomposition are extended to nested relations and an extended chase procedure is defined to test the satisfaction of the data dependencies.