Relation pm#relation_to_set_or_class (*,pm#set_or_class)
  subtype:  sumo#closed_on  sumo#reflexive_on  sumo#irreflexive_on  sumo#partial_ordering_on  sumo#total_ordering_on  sumo#trichotomizing_on  sumo#equivalence_relation_on  pm#relation_to_class  pm#relation_to_another_set_or_class
  supertype:  pm#relation_to_collection (*,pm#collection)
     supertype:  pm#relation_from/to_thing_of_common_kind (*)  this type permits to categorize relations according to their signatures and hence offers (i) a concise way to set essential exclusion relations, and (ii) a systematic and easy-to-follow categorization
        >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
     supertype:  pm#what_relation (*)
        supertype:  pm#wh-/how_relation (*)  this type permits to categorize relations according to the usual who/what/why/where/when/how questions ; this is a traditional but very subjective and ineffective way of categorizing relations 
           >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type