Stray thought on #ontology . In rpg's famous essay he points out that a goal of #objectOriented design is compression. If class B and class C have slots in common, we can write the common slots in a shared superclass A and derive both class B and class C from class A to avoid duplicating ~ontology in both class B and class C.
But if I have two ontologies 𝛽 and 𝛾 it is interesting to check their overlap, but it would be obtuse to introduce a superclass 𝛼 with no real meaning for that duality.