Medical research but also quality management is based upon medical data. The integration, validation, processing, and exploration of this data is known to be a technical obstacle for researching medical domain experts and a major pitfall to (bio-)medical research projects. To overcome this pitfall and actively support the medical domain expert in these tasks, we present an ontology-based clinical data warehouse for scientific research. It is completely generic and adapts itself at run-time to the current domain-ontology, which can be freely defined by the domain expert and describes the actual field of research. The whole system adapts is appearance and behavior to this central ontology and appears to the user like a custom made solution. Furthermore, the elaborate structural meta-information from the ontology is used to actively support the user in tasks that usually require profound IT knowledge, such as defining complex search queries or data quality constraints, or applying advanced data visualization algorithms to the data. The proposed warehouse supports the domain expert trough the whole process of knowledge discovery from data integration to exploration.