Overview of the prototype system. User interface (UI), inference program, and visualization program were implemented in Prolog and JAVA. The ontology (DIO) was divided into three OWL files. 1) Class hierarchy and commonly used instances are stored in dio_event.owl. 2) Instances about irinotecan and its pathway are stored in dio_cpt-11.owl. 3) Instances about ketoconazole and its pathway are stored in dio_KCZ.owl.