The ultimate goal of our research projects on ontology is to give the full picture of theory of knowledge. To make improvements in the study of this difficult issue, of course, it is important to accumulate huge amount of "contents", and develop sophisticated ontology representation language as fundamental "form" of knowledge. In the research project on the latter issue, we have been investigating the variety of fundamental topics concerning ontology, for example,
Based on the analysis, we have been developing an ontology representation language.