EXECUTIVE SUMMARY Enterprises need data resources that are stable and at the same time flexible to support current and new ways of doing business. However, there is a lack of understanding how flexibility of a Conceptual Schema design is demonstrated in its evolution over time. This case study outlines the evolution of a highly integrated Conceptual Schema in its business environment. A gradual decline in schema quality is observed: size and complexity of the schema increase, understandability

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... nd consistency decrease. Contrary to popular belief, it is found that changes aren't driven only by 'accepted' causes like new legislation or product innovation. Other change drivers are identified like error correction, changing perceptions of what the information need of the business is and elimination of derived data. The case shows that a real Conceptual Schema is the result of 'objective' design practices as well as the product of negotiation and compromise with the user community. BACKGROUND Justification Many large application systems in government, banking, insurance and other industries are centered around a relational database. A central component is its Conceptual Schema, being the linking pin between information requirements and perceptions of 'reality' as seen by users, and the way how the corresponding data are actually stored in the database. As user requirements can and will evolve over time, it must be expected that changes to the Conceptual Schema (CS) become necessary. Nevertheless, it is often assumed that superior quality of the initial design is sufficient for it to remain stable over the entire information systems lifecycle. Thus, the ability to adapt to later changes in the user requirements is taken for granted, if not blatantly ignored in most design methods. This case looks at the cumulative effects of a series of changes on the overall quality of a CS, by tracing the actual evolution of one CS in its natural business environment. Although we do describe the separate change step, we don't intend to study or criticize the individual change projects or the realization of strategic targets. Our aim is to develop an overall understanding of successive changes 1331 E.