What is an ontology?

An ontology is a group of concept definitions that describe the structure of information associated to what exists or might exist. An ontology can be expressed in a language that allow semantic content to be processed by computer systems and understandable by humans, examples of such languages include OWL, DAML+OIL and KIF. Ontologies have their origin in Ontology which is a branch of philosophy with more than 2000 years of efforts. Aristotle's categories constitute some of the first ontologies ever proposed. In Ontology, the study of "what" exists or might exist produces theories composed of categories and structures of objects, properties, processes and relations, which are also components of modern computer-processable ontologies. Historical records show that the first use of the term ontology (ontologia) dates back to 1613.

There are multiple reasons that motivate the development of ontologies. Among them we can list the following:

1. To share common understanding of the information that is communicated among people (textbooks, new education approaches) and among software agents
2. To enable reuse of domain knowledge
3. To describe unambiguous definitions that software and people can understand