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Efficient methods of processing unanticipated queries are a crucial prerequisite for the success of generalized database management systems. A wide variety of approaches to improve the performance of query evaluation algorithms have been proposed: logic-based and semantic transformations, fast implementations of basic operations, and combinatorial or(More)
Database queries explicitly containing existential and universal quantification become increasingly important in a number of areas such as integrity checking, interaction of databases and AI systems, heterogeneous databases, and statistical databases. Using a concept of range nesting in relational calculus expressions, the paper describes evaluation(More)
The goal of this paper is to present framework technologies from another perspective: Component technology and framework concepts as a solution for providing tailorability at the user level. We introduce and discuss groupware as one application domain where tailorability is a critical issue and present the framework based architecture of our group editor(More)
Problem based learning aims at providing knowledge applicable to real-world situations. In our project PLI we employ problem based learning in the specific domain of computer science education. We identify the design and introduction of IT infrastructure into organizations as a major task of computer science professionals. From this field we have provided(More)
Component technology and framework concepts are seen as the solution to typical engineering problems that emerge when building groupware. In this paper we introduce and discuss group editors as one example for the nee for component based design in the groupware application domain. We first outline the requirements for group editor applications and show how(More)