Technical reports

Views and imprecise information in databases

Mike Gray

November 1982, 119 pages

This technical report is based on a dissertation submitted November 1982 by the author for the degree of Doctor of Philosophy to the University of Cambridge.

DOI: 10.48456/tr-38

Abstract

Providing user views of a database is an important way of achieving data independence and ease of use of DBMSs. This dissertation discusses one aspect of the problem of supporting views. It is shown that a crucial factor in the support of views is the richness of the data model used, and in particular its ability to represent certain kinds of incomplete information. This dissertation discusses various ways of handling incomplete information, and the operations on views that can be supported. The implementation of an experimental system which supports views on a relational database is described.

The first chapter describes the problem of treating views as first-class objects, that is allowing all the usual database operations to be performed on data in views. It is shown how this is related to the problem of representing incomplete information in the conceptual schema. The second chapter proposes the use of lattices to represent incomplete information, and shows how this covers various particular kinds of imprecise information. The third chapter reviews other work relating to imprecise information in databases. The fourth chapter discusses certain further implications of representing imprecise information, and makes proposals regarding the interpretation of keys, constraints, and the open-world assumption in this environment. The fifth chapter discusses in detail the relational operations that are appropriate with imprecise data and proposes modified Join and Group-by operations. The implementation of a system with these features is discussed. Chapter six illustrates some of the points made by considering an example database, and finally chapter seven concludes this dissertation with a summary and examination of further possibilities.

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BibTeX record

@TechReport{UCAM-CL-TR-38,
  author =	 {Gray, Mike},
  title = 	 {{Views and imprecise information in databases}},
  year = 	 1982,
  month = 	 nov,
  url = 	 {https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-38.pdf},
  institution =  {University of Cambridge, Computer Laboratory},
  doi = 	 {10.48456/tr-38},
  number = 	 {UCAM-CL-TR-38}
}