Table 1 Layer cake assignments for OBO constructs

OBO Core: id, idspace, relationship

OBO Vocabulary: name, definition, comment, is_a, domain, range

OBO Ontology Extensions: format-version, version, date, saved-by, auto-generated-by, namespace, default-namespace, subsetdef, alt_id, relationship, subset, synonym, is_obsolete, is_cyclic, is_transitive, is_symmetric, import, synonymtypedef, intersection_of, union_of, disjoint_from, replaced_by, consider, inverse_of, transitive_over