Relation sumo#relative_time_fn (?,?)
  type:  pm#binary_function_type  class of functions requiring two arguments
  type:  pm#total_valued_relation_type  when there exists an assignment for the last argument position of the relation given any assignment of values to every argument position except the last one; note that declaring a relation to be both a total_valued_relation and a single_valued_relation means that it is a total function
  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