Ontologies play a key role in the realization of the Semantic Web. An ontology is used as an explicit specification of a shared conceptualization of a given domain. When such a domain evolves, the describing ontology needs to evolve too. In this paper, we present an approach that allows tracing evolution nstance level. We use event types as an abstraction mechanism to define the semantics of changes. Furthermore, we introduce a new event-based approach to keep depending artifacts consistent with a changing instance base.