Abstract. In this article we describe a semantic extension of event-driven process chains, with which it is possible to specify the semantics of individual model elements as it is indicated by their label in natural language using concepts of a formal ontology. To do so, a multi-level approach was developed, which comprises an ontology level, a metadata level, as well as a model level. With the approach presented here, ambiguity that is introduced by the use of natural language in semi-formal models can be removed. Moreover, new possibilities of reasoning over business process models are introduced which improve the analysis, search and validation of business processes.1