Relation dl#p_spatial_location__pspatiallocation (perdurant,space_region)
  inverse:  p_spatial_location_of
  supertype:  exact_location__exactlocation (entity,region)
     supertype:  generic_location__genericlocation (entity,entity)
        supertype:  mediated_relation (entity,entity)
           supertype:  conceptual_relation (entity,entity)
              supertype:  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:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type