Relation pm#similar (?,?)  DO NOT USE SUCH A RELATION TYPE DIRECTLY
  supertype:  pm#equivalence_relation__equivalencerelation  this category only serves structuration purposes: it is instance of pm#equivalence_relation_type which is not instance of pm#class_of_inheritable_relation_type
  equal:  nsm#like
  subtype:  pm#closely_similar__closelysimilar (?,?)  the '~' link in WebKB-2: currently only used between categories for Greek gods and their Roman counterparts, and between some types from the 3D (endurantist) approach and their counterparts from the 4D (perdurantist) approach or the ?D (vague/unspecified) approach)
  subtype:  pm#loosely_similar__looselysimilar (?,?)
  subtype:  pm#related_to__relatedto (?,?)  the '&' link in WebKB-2 (currently used for representing a sumo#related_internal_concept relation)
     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