Relation pm#related_to__relatedto (?,?)  the '&' link in WebKB-2 (currently used for representing a sumo#related_internal_concept relation)
  supertype:  pm#similar  DO NOT USE SUCH A RELATION TYPE DIRECTLY
  related_to:  sumo#related_external_concept (pm)
  subtype:  sumo#related_internal_concept (?,?)  the two arguments are related concepts within the SUMO, i.e. there is a significant similarity of meaning between them; to indicate a meaning relation between a SUMO concept and a concept from another source, use sumo#related_external_concept