More details on obo format:

http://owlcollab.github.io/oboformat/doc/obo-syntax.html

In particular, this module provides:

• A graph-like view over an ontology via is_a/2 and relationship/3
• the obo synonym model: entity_synonym_scope/3
• the obo xref model: entity_xref/2 is re-exported from obo_metadata/oio; additional convenience preds such as entity_xref_src/4

 is_a(?A, ?B) is nondet

subClassOf between two names classes

 relationship(?E, ?R, ?O) is nondet

true if E subClassOf R some O

 is_dangling(?E) is semidet

true if E has no label

 entity_synonym_scope(?E, ?V) is nondet

 entity_synonym_scope(?E, ?V, ?Scope) is nondet

true if V is a synonym for entity E, with a Scope of either: exact, broad, narrow, related

 entity_synonym_scope_type(?E, ?V, ?Scope, ?Type) is nondet

As entity_synonym_scope/3 but also include the synonym type

 entity_synonym_scope_xref(?E, ?V, ?Scope, ?Xref) is nondet

As entity_synonym_scope/3 but also include the xref provenance for the synonym

 entity_xref_src(?Cls:atm, ?X:str, ?S:str)

true if Cls has X as an xref, and axiom annotated with S

 entity_xref_prefix(?Cls:atm, ?X:str, ?Pre:str)

true if Cls has X as an xref, and X has prefix Pre

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 synprop_scope(Arg1, Arg2)

 entity_synonym_scope(Arg1, Arg2, Arg3)

 entity_xref_src(Arg1, Arg2, Arg3, Arg4)

 has_dbxref(Arg1, Arg2)