An Extension of the Environment for Building/Using Ontologies Hozo'' toward Practical Ontology Engineering - Focused on Theoretical Issues

Abstract

Recently, ontology has attracted attention as an important technology for knowledge infrastructure and semantic processing, and a lot of ontologies have been constructed in various domains. At the same time, ontological theories, technologies, and ontology engineering tools have been developed by not only researchers but also practitioners. We also have been investigating ontological theories and developed a computer environment for building/using ontologies named ``Hozo'' which is based on the ontological theory of roles. Hozo has been used for practical ontology construction in various domains such as clinical medicine, bioinformatics, environmental engineering and so on. These practices of ontology development have raised many issues of ontology construction and utilization in both theoretical and technical points of view. We have solved them by extending our theories and functions of the system. It means we refined usability and reliability of Hozo through these practical experiences. In this paper, we focus on theoretical issues of ontology construction and discuss some extensions of ontological theories concerning representation of multiple inheritance and instances. First, we introduce IS-A relation which represents a relation weaker than is-a relation in the sense that it prohibits inheritance of identity, and we allow users to represent multiple inheritance using not usual strong is-a relation but IS-A relation. Then we investigate the validity of the representation using IS-A through ontological analysis of three utilization patterns of it. Next, we introduce two kinds of new representation of instances: ``simplified instance representation'' and ``#-(species) operator''. Users can use these representations for referring to instances in concept (class) definitions. These theoretical extensions would contribute to well-organized construction of ontologies in practical ontology engineering.