Relation pm#relation_from_description_content/medium/container (description_content/medium/container,*)
  exclusion:  relation_from_situation  spatial_relation_from_entity_with_spatial_feature  relation_from_collection  relation_from_attribute_or_quality_or_measure
  subtype:  relation_from_description  relation_from_string  version  version_id  Coverage  Contributor  Source  Publisher  Rights  authoring_time  author  Language  Format  description_instrument  description_object  physical_support  rhetorical_relation  argumentation_relation
  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