Merging inheritance hierarchies with overlapping class extensions and types is an essential task in database design. In the context of view integration and schema integration for federated databases and multidatabases conflicting inheritance hierarchies have to be merged. Inheritance hierarchies often occur explicitly in object-oriented databases as well as implicitly in relational databases. Since a concept lattice can be regarded as an inheritance hierarchy we propose to apply the theory of concept analysis to the problem of merging inheritance hierarchies. After investigating the power and complexity of concept analysis algorithms we provide a new algorithm tailored to our problem. The new algorithm has polynomial complexity and helps to optimize the resulting hierarchy with respect to certain quality criteria, e.g., number of classes and null values. An example demonstrates the practicability of our approach to merge conflicting inheritance hierarchies.
Besides this technical part, the talk will give a short overview on projects in the area of database federations at the Computer Science department at the University of Magdeburg.
Gunter Saake was born in 1960 in Göttingen, Germany. He received
the diploma and the Ph. D. degree in computer science from the
Technical University of Braunschweig, F. R. G., in 1985 and 1988,
respectively. From 1988 to 1989 he was a visiting scientist at the IBM
Heidelberg Scientific Center where he joined the Advanced Information
Management project and worked on language features and algorithms for
sorting and duplicate elimination in nested relational database
structures. In January 1993 he received the Habilitation degree (venia
legendi) for computer science from the Technical University of
Braunschweig. Since May 1994, Gunter Saake is full professor for the area
"Databases and Information Systems" at the
Otto-von-Guericke-University Magdeburg . From April 1996 to March
1998, he was dean of the faculty for computer science
Otto-von-Guericke-University Magdeburg .
Gunter Saake participated in a national project on object bases for experts and in the European BRA working groups IS-CORE, ModelAge, ASPIRE and FIREworks . His research interests include conceptual design of data base applications, query languages for complex data base structures and languages, semantics and methodology for object-oriented system specification and application development in distributed and heterogeneous environments. He is member of ACM, IEEE Computer Society, EATCS, GI and of the organization committees of GI FG 2.5.1 `Databases' and GI AK `Foundations of Information Systems'. Besides being author and co-author of scientific publications, he is author of a book "Object-oriented Modelling of Information Systems", co-author of a lecture book on Database Concepts , a lecture book on Object Databases and a book on Building efficient applications using Oracle8 (all in German).