Null Values Revisited in Prospect of Data Integration

  • Guy de Tré
  • Rita de Caluwe
  • Henri Prade
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3226)


A considerable part of the information available in the real world is inherently imperfect and/or incomplete. Traditionally, the most commonly adopted modelling approaches for dealing with imperfect and missing information are based on the use of default values and of null values. However, in order to deal with imperfect information in a more efficient way, a database system needs some more advanced modelling facilities that better reflect the semantics of the data. Such facilities become even more necessary if data stemming from different data sources must be integrated in a distributed, federated database system. In this paper, the concept of a ‘null’ value has been revisited. A semantically richer definition, based on possibility theory, is proposed together with a description of the accompanying many-valued logic. Additionally, the potentials of the new approach with respect to the integration of data in multi-database environments or grid database services are illustrated.


Null values many-valued logic data semantics database modelling data integration 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • Guy de Tré
    • 1
  • Rita de Caluwe
    • 1
  • Henri Prade
    • 2
  1. 1.Computer Science Laboratory, Department of Telecommunications and Information ProcessingGhent UniversityGentBelgium
  2. 2.Institut de Recherche en Informatique de Toulouse (IRIT)–CNRSUniversité Paul SabatierToulouse CedexFrance

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