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    Default databases and incomplete information

    King, Peter J.H. and Small, C. (1991) Default databases and incomplete information. The Computer Journal 34 (3), pp. 239-244. ISSN 0010-4620.

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    We present the concept of a default database which comprises a set of facts, a set of deduction rules, and a set of defaults. Defaults define assumptions to be made about information not derivable from the rules and facts. Defaults, by augmenting the information which is a consequence solely of the rules and facts, enable definite responses to queries on the basis of ‘common sense’ assumptions rather than responses of the form ‘unknown’. The augmented information is termed an extension. Although such an extension is self-consistent, in general two or more mutually inconsistent extensions can arise. We characterise the rules and defaults of a database as safe if only one extension can arise for any given set of facts. We give conditions which are necessary and sufficient to ensure safety.


    Item Type: Article
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Computing and Mathematical Sciences
    Depositing User: Sarah Hall
    Date Deposited: 04 May 2021 16:48
    Last Modified: 09 Aug 2023 12:50


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