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