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The increasing power of modern computers is steadily opening up new
application domains for advanced data processing such as engineering
and knowledge-based applications. To meet their requirements,
concepts for advanced data management have been investigated during
the last decade, especially in the field of object orientation. Over
the last couple of years, the database group at the University of
Kaiserslautern has been developing such an advanced database system,
the KRISYS prototype. In this article, we report on the results and
experiences obtained in the course of this project. The primary
objective for the first version of KRISYS was to provide semantic
features, such as an expressive data model, a set-oriented query
language, deductive as well as active capabilities. The first KRISYS
prototype became completely operational in 1989. To evaluate its
features and to stabilize its functionality, we started to develop
several applications with the system. These experiences marked the
starting point for an overall redesign of KRISYS. Major goals were
to tune KRISYS and its query-processing facilities to a suitable
client/server environment, as well as to provide elaborate
mechanisms for consistency control comprising semantic integrity
constraints, multi-user synchronization, and failure recovery. The
essential aspects of the resulting client/server architecture are
embodied by the client-side data management needed to effectively
support advanced applications and to gain the required system
performance for interactive work. The project stages of KRISYS
properly reflect the essential developments that have taken place in
the research on advanced database systems over the last years.
Hence, the subsequent discussions will bring up a number of
important aspects with regard to advanced data processing that are
of significant general importance, as well as of general
applicability to database systems.
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