Aspects of the Taxonomic Relation in the Biomedical Domain

Taxonomies are commonly used for organizing knowledge, particularly in biomedicine where the taxonomy of living organisms and the classification of diseases are central to the domain. The principles used to produce taxonomies are either intrinsic (properties of the partial ordering relation) or added to make knowledge more manageable (opposition of siblings and economy). The applicability of these principles in the biomedical domain is presented using the Unified Medical Language System (UMLS) and issues raised by the application of these principles are illustrated. While intrinsic principles are not challenged, we argue that the opposition of siblings brings to bear excessive constraints on a domain ontology and that the adverse effects of economy may outweigh its benefits. The two-level structure used in the UMLS is discussed.