What is Ontology?

Ontology is the philosophical study of being, existence, and reality. In information science, an ontology is a formal representation of knowledge as a set of concepts within a domain and the relationships between those concepts.

Ontologies provide a shared vocabulary for modeling a domain, including the types of objects and concepts that exist and their properties and relationships.

Contemporary ontology is an interdisciplinary field. On one hand, ontological research involves philosophers who aim to describe broad categories of entities and their most fundamental relationships. On the other hand, ontologists work in various areas of computer and information science to create more narrowly focused classification systems in domains like bioinformatics, engineering, defense, and security.

Ontologists have developed a wide range of theories and methods to support the consistent representation of data and information using such classifications, known as "ontologies." In all such cases, when data are annotated using well-structured ontologies, they can be more easily retrieved, integrated, and compared—and more effectively used for computer-based reasoning.

In biology and biomedicine, for example, ontologists have developed controlled vocabularies such as the Gene Ontology to describe the results of biological experiments in a consistent way. This allows for comparison across species, diseases, and biological systems. In government, administration, and commerce, ontologies are also used to connect data across departments (such as large government agencies) and to make these data accessible to standard software tools.

Ontologists study how definitions, classifications and relationships should be formulated using the tools of logic and formal semantics in order to most effectively achieve these goals. Their research provides foundations for diverse technologies in areas such as information integration, natural language processing, data annotation, and the construction of intelligent computer systems. Ontologies can also be used by human beings to codify and make explicit common understandings that support human-to-human communication and successful collaborative research across disciplinary boundaries.