Abstract Using roles in object‐oriented design leads to a more natural representation of a given problem domain. Despite a lot of research into role–based systems, there is still a gap between conceptual representations of roles and the usage of roles in strongly typed object‐oriented programming languages such as C++ or Java. Since these languages associate classes and their instances exclusively and permanently, representing evolving objects that may take on different roles over time is difficult without special support: (i) entities must be reclassified any time they evolve and (ii) class hierarchies may grow exponentially if entities may take on several independent roles. This article shows how role hierarchies can be easily implemented in Java. It introduces the Java Role Package, which provides a set of classes to support handling of evolving objects without modifying the semantics of Java itself. Copyright © 2004 John Wiley & Sons, Ltd.

Abstract Active data warehouses belong to a new category of decision support systems, which automate decision making for routine decision tasks and semi‐routine decision tasks. Just as active database systems extend conventional database systems with event–condition–action rules for integrity constraint enforcement or procedure execution, active data warehouses extend conventional data warehouses with analysis rules that mimic the work of an analyst during decision making. This paper demonstrates how analysis rules can be implemented on top of a passive relational data warehouse system by using commercially available database technology. Copyright © 2002 John Wiley & Sons, Ltd.

At the conceptual level, business rules are formulated from an external observation perspective according to the event-condition-action structure of rules in active database systems. Situation/activation diagrams homogeneously extend object/behavior diagrams to a graphical notation for the conceptual design of business objects and their associated business rules. Situation diagrams provide a high-level representation of logical events. Activation diagrams specify graphically which activities have to be performed upon some triggering event if an associated condition is satisfied. The developed editor supports both object/behavior diagrams and situation/activation diagrams. The editor performs syntactic consistency checks during the interactive design process. Moreover, by building the logical model in parallel with the diagrams, the editor guarantees that local semantic consistency checks can be performed incrementally, too. The editor clearly separates between schema data and pure visualization data describing the location of diagram elements. This separation facilitates the reuse of the generated data for further processing. Both schema data and visualization data are stored in the commercial object-oriented database system GemStone. Alternatively, those data may be stored in a file. The editor has been implemented using VisualWorks and MetaDoME, a framework for building graphical editors with VisualWorks.