Relation pm#later_situation__latersituation (situation,situation)
  supertype:  relation_from_situation_to_situation  before
  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