Relation pm#why_relation__whyrelation (*)
  supertype:  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 
  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
  subtype:  consequence (situation,situation)  see also rst#effect
  subtype:  method (process,description)
  subtype:  goal (process,situation)
  subtype:  triggering_event (process,event)
  subtype:  ending_event (process,event)
  subtype:  precondition (process,situation)
  subtype:  postcondition (process,situation)
  subtype:  purpose (?,?)
     subtype:  goal (process,situation)
     subtype:  purpose (description_content/medium/container,description_content/medium/container)  situation that the described action is intended to reach