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.
