Relation nsm#before (?,?)
  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:  before (time_measure,time_measure)
  subtype:  before_time (situation,time_measure)
  subtype:  later_situation__latersituation (situation,situation)
     subtype:  next_situation (situation -> situation)
        subtype:  successor (situation -> situation)
     subtype:  ending_situation__termination (situation -> situation)
     subtype:  postcondition (process,situation)
     subtype:  consequence (situation,situation)  see also rst#effect