Relation pm#symmetric_relation__symmetricrelation (?,?)  this category only serves structuration purposes: it is instance of pm#symmetric_relation_type which is not instance of pm#class_of_inheritable_relation_type
  supertype:  binary_relation_with_particular_mathematical_property
  instance of:  symmetric_relation_type
  subtype:  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
     subtype:  similar (?,?)  DO NOT USE SUCH A RELATION TYPE DIRECTLY
        subtype:  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:  loosely_similar__looselysimilar (?,?)
        subtype:  related_to__relatedto (?,?)  the '&' link in WebKB-2 (currently used for representing a sumo#related_internal_concept relation)
           subtype:  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
     subtype:  equal (?,?)  "=" in KIF; true if the 1st argument is identical to the 2nd
        subtype:  same_as (?,?)  MORE PRECISE TYPES THAN THIS ONE SHOULD BE USED
           subtype:  same_type_as (type,type)
              subtype:  equivalent_class (class,class)  in WebKB, use the link '='
              subtype:  equivalent_property (binary_relation_type,binary_relation_type)  in WebKB, use the link '='
           subtype:  same_individual_as (?,?)
     subtype:  equivalence__equivalentTo___iff__iff (description,description)
     subtype:  copy (object,object)  relates an object to an exact copy of the object, where an exact copy is indistinguishable from the original with regard to every property except (possibly) spatial and/or temporal location
     subtype:  equivalent_content_class (?,?)
     subtype:  equivalent_content_instance (?,?)
     subtype:  cooccur (?,?)
     subtype:  family_relation (?,?)
  subtype:  different__different_from__differentfrom (?,?)
     subtype:  different_from__differentfrom (?,?)
     subtype:  exclusive_class__exclusiveclas (class,class)  the 2 classes have no common subtype/instance; in WebKB, use the link '!'
        subtype:  complement_class (class -> class)  if something is not in one of the classes, then it is in the other, and vice versa; in WebKB, use the link '/'
  subtype:  independent_probability__independentprobability (formula,formula)  the probabilities of the formulas being true are independent
  subtype:  overlaps_temporally (?,?)
  subtype:  connected (object,*)
  subtype:  meets_spatially__meetsspatially (?,?)
  subtype:  overlaps_spatially (?,?)
  subtype:  overlaps_partially (?,?)
  subtype:  connected_engineering_components (?,?)
  subtype:  sibling (?,?)
  subtype:  legal_relation__legalrelation (?,?)
  subtype:  spouse (?,?)
  subtype:  consistent (?,?)