BIROn - Birkbeck Institutional Research Online

    The nested relation type model: an application of domain theory to databases

    Levene, Mark and Loizou, G. (1990) The nested relation type model: an application of domain theory to databases. The Computer Journal 33 (1), pp. 19-30. ISSN 0010-4620.

    Full text not available from this repository.

    Abstract

    To date 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, in addition to system-defined null types, user-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 nester-relations types and a partial order 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 supersede known algebras for relations with nulls and for nested relations by showing faithfulness to these algebras. We then investigate the 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 information content of the user's view, which is constructed from an algebraic expression over the instances in the database. Finally, we enhance the expressive power of the NRT-algebra with a least fixpoint operator in order to allow users to pose recursive queries.

    Metadata

    Item Type: Article
    School: School of Business, Economics & Informatics > Computer Science and Information Systems
    Depositing User: Sarah Hall
    Date Deposited: 15 Jun 2021 17:10
    Last Modified: 15 Jun 2021 17:10
    URI: https://eprints.bbk.ac.uk/id/eprint/44743

    Statistics

    Downloads
    Activity Overview
    0Downloads
    16Hits

    Additional statistics are available via IRStats2.

    Archive Staff Only (login required)

    Edit/View Item Edit/View Item