Ontologies are shared conceptualizations of a domain. As this domain may change over the time, the ontology has to evolve as well. Additionally, for many applications, it is important to know which version of an ontology was valid at a certain point in time. Several ontology version management systems address this problem. If a user is confronted with different versions of an ontology it is often necessary to identify the changes. We present an efficient graph based approach for change

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... between two versions of an ontology based on structural comparisons. The result is a change script transforming the old to the new version. Furthermore, we present an extensive evaluation of the prototype implementation of the change detection system.