The use of ontology within bioinformatics is relatively recent and consequently there are not a large number in existence. In this section, a representative sample of existing bio-ontologies will be reviewed. This survey has been restricted to those ontologies most pertinent to current trends in bioinformatics and molecular biology, rather than the wider field of biology. Biology is rich in taxonomies, such as the Enzyme Classification [12] and species taxonomies. Being taxonomies, they only use a subsumption hierarchy. The ontologies reviewed here tend to be richer in their use of relationships, hence their inclusion, but this is not to denigrate the usefulness of taxonomies to many applications. The ontologies reviewed are as follows:
