Prolog-based Implementation of a Straightforward NF2 Relational Query Interface
Timo Niemi# and Kalervo Järvelin+
#Department of Computer Science
+Department of Information Studies
University of Tampere
P.O.Box 607
FIN-33101 TAMPERE, Finland
REFERENCE
Abstract
It has been widely recognized that the proposed user-oriented NF2 (Non-First-Normal-Form) relational query languages such as different SQL extensions are cumbersome to use from view point of an ordinary end-user. This is because the user usually has to formulate large nested expressions in order to specify how the result NF2 relation is derived from the source NF2 relation(s). The NF2 relational query interface in this paper is based on a different approach. In it the user describes only the structure of the result NF2 relation in a straightforward and intuitive way. This starting point of our interface affords the possibility of formulating queries in a compact and truly declarative manner - also in those cases which require considerable restructuring among data. In this paper we consider the Prolog-based implementation of the query processing strategy of our interface. Special attention is paid to those principles and techniques in terms of which the representation and manipulation of complex structural relationships of NF2 relations can be managed in Prolog. The representation of NF2 relations and the query processing strategy have been designed to support main memory oriented implementation.
Keywords: NF2 relational model, User interface, Query processing, Logic programming, Prolog-based knowledge representation.
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