This work presents a fully elaborated ontology, defined via the Ontology Web Language (OWL), of the Business Process Model and Notation (BPMN) standard to define business process models, and we demonstrate that any BPMN model can be serialized as OWL file. Based on ontological analysis and a corresponding definition of a modeling notation as ontology we show that business process models can be transformed from one notation into another one as long as there are common underlying concepts; this is demonstrated with the case of an actor based, or subject-oriented, view on business processes. Furthermore, a reference architecture for Workflow Management Systems (WfMS) based on microservices is discussed which is capable of executing actor based business process models. As a transformation of BPMN models into the actor based view is generally possible, also BPMN models could be enacted. As a result, we can conclude that the actor system is a promising way to stimulate new ways to design workflow management systems and to design business process modeling languages which are more comfortable to use by non-experts without losing necessary expressiveness. Another result is that an ontology is a productive way to define a modeling notation as it can be used as knowledge base, it is a formal conceptualization of the underlying notions, and can be semantically enriched for further use.