Relation pm#mereological_relation (?,*)
  exclusion:  pm#attributive_relation  pm#intentional_relation  pm#temporal_relation  pm#object_relation
  subtype:  pm#part_or_parts  pm#part_of  pm#overlap_with
  supertype:  pm#relation_playing_a_special_role (*)  this type permits to categorize relations according to their roles ; this is a traditional but quite subjective 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
  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