Relation sumo#synonymous_external_concept (string,?,language)  the 2nd argument has the same meaning as the 1st in the language denoted by the 3rd argument
  exclusion:  subsumed_external_concept  subsuming_external_concept
  supertype:  related_external_concept (string,?,language)  used to signify a three-place relation between a concept in an external knowledge source, a concept in the SUMO, and the name of the other knowledge source
     supertype:  relation_from_string (string,*)
        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