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E. Zimányi. Incomplete and Uncertain Information in Relational Databases. PhD thesis, Université libre de Bruxelles, Brussels, Belgium, October 1992.

Abstract

In real life it is very often the case that the available knowledge is imperfect in the sense that it representes multiple possible states of the external world, yet it is unknown which state corresponds to the actual situation of the world. Imperfect knowledge can be of two different categories. Knowledge is incomplete if it represents different states, one of which is true in the external world. On the contrary, knowledge is uncertain if it represents different states which can be satisfied or are likely to be true in the external world. The study of imperfect knowledge has been an active area of research, in particular in the context of relational databases. However, due to to the complexity of manipulating imperfect knowledge, little practical results have been obtained so far. In this thesis we provide a survey of the field of incompleteness and uncertainty in relational databases. The rest of the thesis studies in detail the manipulation of one type of incomplete knowledge, namely disjunctive information, and one type of uncertain information, namely probabilistic information. We study both types of imperfect knowledge using similar approaches, that is through an algebraic and a logical framework. A major implication of these studies is the conviction that viewing incompleteness and uncertainty as different facets of the same problem would allow a deeper undertanding of imperfect knowledge, which is absolutely necessary for building information systems capable of modeling real-life situations.


Updated: 2017-03-27