This paper presents an ontological analysis of the EPC (Eventdriven Process Chain) business process modeling notation supported in the ARIS Toolset. This ontological analysis provides an interpretation of the modeling elements in EPC diagrams in terms of the UFO foundational ontology. This enables us to define the precise real-world semantics for business process models represented through EPCs and allows us to identify problems affecting the clarity and expressiveness of EPCs. In our analysis, we consider an up-to-date metamodel of the ARIS Method that we have defined in our earlier work, which specifies EPCs as currently supported by the ARIS Toolset. To the best of our knowledge, the interpretation proposed here is presently the most complete ontological account for EPCs. Keywords Business Process Modeling, Event-Driven Process Chains (EPCs), ARIS, Ontological Analysis, Foundational Ontologies.