Given a set of ontologies S, for each ontology, O, in S, this change combines
multiple subclass axioms with a common left hand side into one subclass
axiom. For example, given A subClassOf B, A subClassOf C, this change will
remove these two axioms and replace them by adding one subclass axiom, A
subClassOf (B and C).
Matthew Horridge, The University Of Manchester, Bio-Health