The more Semantic Web attracts attention, the more importance of ontology increases. Software agents
and people can find information about many domains on the web. And, on each domain or several
domains, ontology can describe what concepts exist in the target world. Many tools for ontology
development have been developed to date. On the other hand, fundamental theories of ontology based on
philosophy have been investigated exhaustively. However, not many of the ontology development tools
provide higher level of constructs for ontology description compliant with the fundamental theories of
ontology. So, it is still difficult to develop a theoretically sound ontology which describes definitions of
concepts properly based on ontological theories. We have developed an environment for building/using
ontologies based on a fundamental consideration of role and relationship [1, 2]. In this research, we aim
to enhance descriptive quality of role-concept in our ontology development system Hozo.
It is indispensable for building ontology to describe properties (or attributes) of concepts. Ontology
languages for the Semantic Web provide some mechanisms to define property for representing roles,
relations, attributes, etc., and most of ontology development tools support them. While those properties
have different semantics according to the theories of ontology, most of the tools do not support users to
develop an ontology which reflects distinctions among them. Even if the users contrive to describe
distinction among the kinds of properties in some way, the descriptions tend to be ad hoc and not be able
to define concepts rightly or naturally in the same way as people understand them. To make it easier to
develop an ontologically-sound ontology, we need a tool with higher level constructs which help us to
differentiate properties and provide a framework for representing such differentiation.