The interrelationship of the ontologies. The interrelationship of the ontologies is based on the notion of the state of an entity, characterized by the four properties: amount, location, dynamics, and physical. This division into four properties is found in three subtrees of the two ontologies: the property and process subtrees of the entity type ontology and the change subtree of the relationship ontology.
Pyysalo et al. BMC Bioinformatics 2007 8:50 doi:10.1186/1471-2105-8-50