Relation pm#ascii_content_except_for_spaces (description_content/medium/container,string)
  supertype:  ascii_content__asciicontent (description_content/medium/container,string)
     supertype:  version (description_content/medium/container,description_content/medium/container)
        supertype:  relation_from_description_content/medium/container (description_content/medium/container,*)
           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