Relation nsm#after (?,?)
  supertype:  binary_relation (pm)  in WebKB, most relation types are binary and some have a variable number of arguments (as in KIF), hence this type is currently only specialized by types that I do not want to see as direct subtypes of pm#relation
  subtype:  after (time_measure,time_measure)
  subtype:  until_time__untiltime__to_time (situation -> time_measure)
     subtype:  arrival_time__arrivaltime (process -> time_measure)
  subtype:  before_situation (situation,situation)  in WebKB, do not use these relations, use their inverses
     subtype:  previous_situation (situation -> situation)
     subtype:  beginning_situation__beginningsituation (situation -> situation)
     subtype:  precondition (process,situation)
     subtype:  cause (situation,situation)  see also rst#cause
        subtype:  causes (process,process)  the process in the 1st argument brings about the process in the 2nd argument