Wenn Ausnahmen zum Normalfall werden: Modellierung struktureller Ausnahmen in Datenbanken

Database systems (DBS) are generic software systems for the reliable administration and use of high volumes of data. The structure of the database is created by designing an appropriate scheme for the particular application (i.e. the domain). The goal is to achieve a precise mapping between the modelled domain and the mini world created in the DBS. Today, there are several approaches to such a design, though all focus solely on the most common case of the domain in question Exceptions, as quite naturally arise, are not handled explicitly by the database structure. In this paper, we introduce examples to illustrate the problem of structural receptions. Subsequently, we present a modelling approach which enables the user to separate exceptions from the common case within the scope of design. We also show how exceptions can be handled explicitly without special assistance of the user.