Joachim Thomas

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This paper focuses on the problems that arise when integrating data from heterogeneous sources in a single, unified database view. At first, we give a detailed analysis of the kinds of structural heterogeneity that occur when unified views are derived from different database systems. We present the results in a multiple tier architecture which distinguishes(More)
Data relationships play a very important role in application domains and thus should be a key issue in database modeling. However, they are still not well considered in the emerging object-relational database (ORDB) technology, where the main concern is put on the extension of the relational data model (RDM) with objects as basic modeling constructs. This(More)
This paper focuses on the architecture of our prototype supporting the integration of heterogeneous data. The main characteristics of our system are its extended schema architecture and the generic translation approach based on a mapping language. At first, we introduce the schema architecture as well as the essential properties of our mapping language. One(More)
As determined by the applications' requirements, non-standard DBMS are usually conceived for client/server architectures [5, 12]. While the server is responsible for general data-management tasks and for precomputing data, application-oriented processing is done in the main-memory buffer at the client. Since the expressive power of the query language should(More)
A great variety of techniques has been developed to optimize and enhance query processing for relational, client/server, distribute~ parallel, and heterogeneous database systems (DBS). Baaed on that work and experience, we investigate how far those techniques are applicable to query processing in Knowledge Base Management Systems (KBMS). Our reference(More)
KRISYS is a prototypical knowledge base management system (KBMS) conceived for clientiserver environments. The server DBMS is responsible for general data management tasks which are carried out in the data model of the server. Processing in the client buffer, termed knowledge processing, is performed in the scope of the object-oriented knowledge model of(More)