In the artificial knowledge field ontology is defined as explicit specification of conceptualization. Ontology engineering is a key method for information technology that can be understood by people and computers. An ontology consists of concepts and relationships that are needed to describe the target world and provides common terms, concepts, and semantics by which users can represent content with minimum ambiguity and interpersonal variation of expression. An ontology is expected to contribute to the structuring of the knowledge in the target world. The construction of a well-designed ontology enables an explicit understanding of the target world. An ontology, however, is identified not by the form of the knowledge, such as description languages and representation forms, but rather by the content of some described knowledge and the roles that the described knowledge plays.
The paper is part of the special issue of the Journal of Hydrology.