Relation sumo#disjoint_decomposition (sumo#class,sumo#class+)  a disjoint_decomposition of a class C is a set of mutually disjoint subclasses of C
  supertype:  pm#relation_to_another_class (pm)
  instance of:  pm#predicate_type (pm)  pm#variable_arity_relation_type (pm)
  related_to:  sumo#exhaustiveDecomposition  sumo#disjoint
  subtype:  sumo#partition (sumo#class,sumo#class+)  a partition of a class C is a set of mutually disjoint classes (a subclass partition) covering C; each instance of C is instance of exactly one of the subclasses in the partition