Although process mining has matured over the last years and many mining techniques are available, several important open problems and challenges are remaining. First, when looking to all four systems of the spectrum, it is clear that data is spread around disparate data sources. Based on the questions posed by the medical professionals, data may be required from different data sources. This requires that links between the four systems of the spectrum are clear. The usage of ontologies is interesting in this respect. Ontologies can be used for defining an appropriate scope and to identify the case from the data sources. Currently, some research is performed in the context of ontologies and (semantic) process mining [3, 20]. Further research should explore opportunities for developing an ontology for process mining systems in the healthcare domain.