A domain theoretic approach to incomplete information in nested relational databases

  • M. Levene
  • G. Loizou
Interfaces And Formal Models
Part of the Lecture Notes in Computer Science book series (LNCS, volume 367)

Abstract

Most previous approaches to incomplete information within the relational model depend on the specific semantics of the null types incorporated into this model. Herein we propose a model for incomplete information in nested relational databases which is independent of the semantics of the null types pertaining to incomplete information. Thus, the proposed model, called the nested relation type (NRT) model, allows user-defined null types, in addition to system-defined null types. The NRT model extends the nested relational model by incorporating a form of built-in inheritance. This allows us to define a partial order between nested-relations types and between the data values of these types. By utilizing these partial orders, we define an instance, over a NRT, to be incomplete when its information content may increase. In addition, we define an algebra for the NRT model, called the NRT algebra, which is shown to supercede known algebras for relations with nulls and for nested relations by showing faithfulness to these algebras. Finally, we investigate monotonicity of the operators of the NRT algebra, which allows us to predict how increasing or decreasing the information content of the instances in the database affects the user's view which is constructed from an algebraic expression over the instances in the database.

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Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • M. Levene
    • 1
  • G. Loizou
    • 1
  1. 1.Department of Computer Science, Birkbeck CollegeUniversity of LondonLondonU.K.

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