Document Server@UHasselt >
Research publications >
Please use this identifier to cite or link to this item:
|Title: ||On a hierarchy of classes for nested databases|
|Authors: ||Gyssens, Marc|
Van Gucht, Dirk
|Issue Date: ||1990|
|Citation: ||INFORMATION PROCESSING LETTERS, 36 (5), p. 259-266|
|Abstract: ||The nested relational model is nowadays generally accepted as a valid alternative to the flat relational model of Codd, because of its greater ability to model the structure of the real world. Not all nested relations however correspond to representations of the real world. Therefore, a hierarchy of more restricted classes of nested relations was defined. For one such class, called hierarchical nested relations (HNR), we give a characterization in terms of closure properties with respect to algebraic operations. For the largest subclass, the normalization-lossless relations (NL), consisting of all relations obtainable from flat relations using restructing operators only, we show membership to be decidable. At the same time, we provide arguments indicating that an efficient algorithm to decide this membership probably does not exist.|
|Type: ||Journal Contribution|
|Appears in Collections: ||Research publications|
Files in This Item:
There are no files associated with this item.
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.