Definitions in Ontologies

Ontologies standardly contain definitions, which can be of two kinds: textual, to help human users understand and correctly use the ontology terms; and logical, to allow automated systems to check the consistency of the ontology, to enhance querying, and to integrate and compare data annotated using the ontology. Textual and logical definitions have overlapping and complementary functions. Both share the linguistic functions of fixing, clarifying, and conveying the intended meaning of terms in the ontology. Both fulfill a cognitive function by enhancing the lexical competence of users when working with the ontology terms whose meanings the definitions specify. In this communication, we examine the different kinds of things to which the term 'definition' refers, and review their linguistic and cognitive functions. We focus on the function of definitions as a means for enhancing the semantic inferential competences of human users and automated systems. We also emphasize functions more specific to definitions in ontologies. Finally, we show how analyzing the relations between textual and logical definitions may be useful for improving the quality of definitions in ontologies.