Introduction to the special issue on advances in ontologies

This special issue of the Expert Systems journal addresses research issues on ontology, an area that is receiving increased attention from researchers on the semantic web. According to Gruber (1993), an ontology is an explicit specification of a conceptualization, i.e. an abstract, simplified view of the world that includes the objects, concepts and the relationships between them in a domain of interest. The use of formal ontologies in knowledge systems has many advantages. It allows an unambiguous specification of the structure of knowledge in a domain, enables knowledge sharing and reuse and, consequently, makes automated reasoning about ontologies possible. In recent years, there has been a worldwide increase in the use of ontologies, both in industry and in research laboratories. This special issue presents the recent advances, both in theory and practical applications, of ontologies to a general audience and provides an opportunity for the broader expert systems community to become aware of current ontology research. There was an overwhelming interest in the general call for papers for the special issue. We received 24 high quality submissions from researchers in Argentina, Australia, Brazil, France, Iran, Japan, Spain, Taiwan, Republic of China, Turkey and the USA. Each submission was sent to at least two reviewers who are experts in ontology research and closely related areas. Although we judged many more submissions to be publishable, we could only include eight papers in the special issue due to time and space limitations. A few high quality papers that we could not accommodate in the special issue were referred to regular issues of Expert Systems. The submissions also included the revised and extended versions of a number of papers selected from among those presented at the Australasian Ontology Workshop (AOW 2006) (Orgun &Meyer, 2006). AOW 2006 was held on 5 December 2006 in conjunction with the 19th Australian Joint Conference on Artificial Intelligence in Hobart, Tasmania, Australia. The purpose of the AOWworkshop series is to bring together ontology researchers from academia and industry in the Australasian region for interaction, discussion, sharing of results and initiation of new projects, and also to raise the awareness of the Australasian artificial intelligence community to state-of-the-art ontology research conducted in the region. This special issue is further testament to the vibrant ontology research conducted within the Australasian region, and its strong connections with the international ontology community. We trust that the breadth and diversity of the papers published in this special issue will foster further research on ontologies ranging from theoretical to practical issues and to applications. The special issue starts off with papers on interoperability in ontologies and ontology merging, alignment and integration. Semantic interoperability between ontologies is essential for enabling communication and sharing of information between heterogeneous systems. The paper by Orgun et al. surveys the main approaches for semantic interoperability between domain ontologies. The authors critically examine various approaches based on the underlying technology used, i.e. agentor non-agent-based, the degree of automation and the use of intermediaries such as lexicons and meta-ontologies. Guest editorial__________________