Relation pm#facility (spatial_object,?)
  supertype:  relation_from_spatial_object (spatial_object,*)
     supertype:  spatial_relation_from_entity_with_spatial_feature (object,*)
        supertype:  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:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type