1 Ontology Engineering Environments

In order to discuss ontology engineering environments, we first need to clarify what we mean by ontology engineering. Ontology engineering is a successor of knowledge engineering which has been considered as a key technology for building knowledge-intensive systems. Although knowledge engineering has contributed to eliciting expertise, organizing it into a computational structure, and building knowledge bases, AI researchers have noticed the necessity of a more robust and theoretically sound engineering which enables knowledge sharing/reuse and formulation of the problem solving process itself. Knowledge engineering technology has thus developed into “ontology engineering” where “ontology” is the key concept to investigate. There is another story concerning the importance of ontology engineering. It is the semantic web movement. Semantic web strongly requires semantic interoperability among metadata which are made using semantic tags defined in an ontology. The issue here is to build good ontologies to come up with meaningful sets of tags which are made interoperable by ontology alignment. Although the importance of ontology is well-understood, it is also known that building a good ontology is a hard task. This is why there have been developed some methodologies for ontology development and have been built a number of ontology representation and editing tools. Among many tools [1,7,8,11,15,16,17,18,19], because of the space limitation, this chapter takes up OntoEdit[15,16], WebODE[1], Protégé[11] and Hozo[7,8] which cover a wide rage of ontology development process rather than being single-purpose tools which are covered elsewhere.