On Roth, Korth, and Silberschatz's extended algebra and calculus for nested relational databases

We discuss the issues encountered in the extended algebra and calculus languages for nested relations defined by Roth, Korth, and Silberschatz. Their equivalence proof between algebra and calculus fails because of the keying problems and the use of extended set operations. Extended set operations also have unintended side effects. Furthermore, their calculus seems to allow the generation of power sets, thus making it more powerful than their algebra

Datalog extension for nested relations

AbstractThe nested relational model allows relations that are not in first normal form. This paper gives an extension of Datalog rules for nested relations. In our approach, nested Datalog is a natural extension of Datalog introduced for the relational data model. A nested Datalog program has a hierarchical structure of rules and subprograms to manipulate relation values of nested relations. We introduce a new category of predicate symbols, the variable predicate symbols to refer to tuples of subrelations. The notion of soundness, safety and consistency is defined to avoid undesirable nested Datalog programs. The evaluation of nested Datalog is given in terms of the nested relational algebra. Finally, we relate the expressive power of nonrecursive nested Datalog to the power of nested relational algebra and safe nested tuple relational calculus

Search and Preference-Based Navigation in Electronic Shopping

The aim of this paper is to address the requirements for electronic shopping systems. Large-scale computerized electronic shopping systems need to accommodate both (a) a large number of products, many of which are close substitutes, and (b) a heterogeneous body of customers who have complex, multidimensional â and perhaps rapidly changing â preferences regarding the products for sale in the system. Further, these systems will have to be designed in a manner so as to both (c) reduce the complexity of the shopping problem from the customerâs point of view, and (d) effectively and insightfully match products to customersâ needs. We show has an abstraction hierarchy with an imposed distance metric provides the necessary elements to implement the desired features. Further, we indicate how the distance metric, in the context of the abstraction hierarchy, can be interpreted as a unidimensional utility function. Finally, we extend the single dimensional (single perspective) treatment to multiple dimensions, or perspectives, and show how the resulting representation can be interpreted as a multiattribute utility function. We argue that the resulting function is plausible and, most importantly, testable.Information Systems Working Papers Serie

Implementation des ATKIS in GIS mit relationaler Attributverwaltung unter dem Aspekt der Fortführung

Das Amtliche Topographisch-Kartographische Informationssystem (ATKIS) ist ein Vorhaben der Landesvermessungsverwaltungen der Bundesrepublik Deutschland zum Aufbau digitaler Landschaftmodelle (DLM) und digitaler Kartenmodelle (DKM). In der Arbeit werden zunächst die Grundideen von ATKIS und von temporalen Datenmodellen dargestellt. Auf Grund einer Analyse des ATKIS-Objektartenkatalogs wurde ein Metainformationssystem DST entwickelt und mit Unterstützung des Instituts für Angewandte Geodäsie / Außenstelle Leipzig (IfAG) praktisch eingeführt. Weiterhin wurden Vorschläge für temporale Erweiterungen des DLM unterbreitet, die insbesondere die Gewinnung inkrementeller Fortführungsinformationen unterstützen