Information-Based Distance Measures and the Canonical Reflection of View Updates

For the problem of reflecting an update on a database view to the main schema, the constant-complement strategies are precisely those which avoid all update anomalies, and so define the gold standard for well-behaved solutions to the problem. However, the families of view updates which are supported under such strategies are limited, so it is sometimes necessary to go beyond them, albeit in a systematic fashion. In this work, an investigation of such extended strategies is initiated for relational schemata. The approach is to characterize the information content of a database instance, and then require that the optimal reflection of a view update to the main schema embody the least possible change of information. The key property is identified to be strong monotonicity of the view, meaning that view insertions may always be reflected as insertions to the main schema, and likewise for deletions. In that context it is shown that for insertions and deletions, an optimal update, entailing the least change of information, exists and is unique up to isomorphism for wide classes of constraints

Raum- und Grenzkonzeptionen in der Erforschung europäischer Regionen

Von historischen und kulturellen Konzeptionen strukturiert, durch politische Grenzen zerstückelt und geprägt von Kooperation und Konflikten sind Grenzräume ein komplexer Untersuchungsgegenstand. Der vorliegende Band versammelt geschichtswissenschaftliche, soziologische, ethnologische und informationswissenschaftliche Zugänge in zwölf Einzelbeiträgen und einer Schreibdiskussion. Neben theoretisch-methodischen Überlegungen stehen epochen- und auch disziplinübergreifend europäische Grenzräume im Fokus. Die Beiträge des Bandes analysieren diese Raum- und Grenzkonzeptionen empirisch fundiert mit Blick auf die soziale Konstruktion des Raums, die rechtlichen Verknüpfungen, die Alltagspraxis der Grenze, die Ausprägungen von Geschichtsbewusstsein und Geschichtskultur und die Inklusions- und Exklusionsdynamiken in verschiedenen Epochen.Borderlands are a complex subject to study. They are structured by various historical and cultural conceptions, fragmented by political borders, and shaped by cooperation and conflict. This volume brings together different approaches from history, sociology, ethnology, and information science. It includes twelve individual contributions and a writing discussion. In addition to theoretical-methodological considerations, the volume focuses specifically on European borderlands across epochs and disciplines. The empirical contributions in this volume analyse conceptions of space and borders with special regard to the social construction of space, legal linkages, praxeology of the border, formation of historical consciousness and historical culture as well as the dynamics of inclusion and exclusion in different epochs