Relation sumo#earlier (?,?)
  type:  pm#binary_predicate_type  the class of predicates relating two items - its valence is two
  type:  pm#irreflexive_relation_type  r is irreflexive if r(?i,?i) holds for no value of ?i
  type:  pm#transitive_relation_type  a binary_relation ?REL is transitive if (?REL ?INST1 ?INST2) and (?REL ?INST2 ?INST3) imply (?REL ?INST1 ?INST3), for all ?INST1, ?INST2, and ?INST3
  type:  pm#temporal_relation_type  the class of temporal relations, e.g., notions of (temporal) topology of intervals, (temporal) schemata, and (temporal) extension
  supertype:  pm#temporal_relation (?,?)
     supertype:  pm#relation_playing_a_special_role (*)  this type permits to categorize relations according to their roles ; this is a traditional but quite subjective way of categorizing relations
        >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
     supertype:  pm#when_relation (?,?)
        supertype:  pm#wh-/how_relation (*)  this type permits to categorize relations according to the usual who/what/why/where/when/how questions ; this is a traditional but very subjective and ineffective way of categorizing relations 
           >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
  supertype:  pm#irreflexive_relation__irreflexiverelation (?,?)  this category only serves structuration purposes: it is instance of pm#irreflexive_relation_type which is not instance of pm#class_of_inheritable_relation_type
     supertype:  pm#binary_relation_with_particular_mathematical_property (?,?)
        supertype:  pm#relation_with_particular_mathematical_property (*)
           supertype:  pm#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:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
  supertype:  pm#transitive_relation (?,?)  this category only serves structuration purposes: it is instance of pm#transitive_relation_type which is not instance of pm#class_of_inheritable_relation_type
     supertype:  pm#binary_relation_with_particular_mathematical_property (?,?)