Relation pm#reflexive_relation__reflexiverelation (?,?)  this category only serves structuration purposes: it is instance of pm#reflexive_relation_type which is not instance of pm#class_of_inheritable_relation_type
  subtype:  equivalence_relation  partial_ordering_relation  overlaps_temporally  connected  overlaps_spatially
  type:  reflexive_relation_type  a relation is reflexive if (?REL ?INST ?INST) for all ?INST
  supertype:  binary_relation_with_particular_mathematical_property (?,?)
     supertype:  relation_with_particular_mathematical_property (*)
        supertype:  relation_with_particular_property (*)  this rather fuzzy type permits to group categorization schemes less common than those covered by the previous sibling categories
           >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type