[...] SBO is a hierarchy of terms developed by the systems biology modelling community to assist compliance with MIRIAM, ensure unambiguous understanding of the meaning of the annotated entities and foster mapping between annotated elements from multiple formats making use of the ontology [10]. By adding SBO terms, modellers take an essential step towards such compliance [3]. Each term in SBO is related to its direct parent with an is a subsumption relationship such as catalyst is a modifier. For a full description of SBO itself and its relationship to other systems biology standards, see Section 1.4. [...] - Allyson Lister