Relation pm#instrument (pm#situation,pm#entity)
  supertype:  pm#object/result  pm#how_relation
  subtype:  sumo#instrument (sumo#process,sumo#object)  the 2nd argument is used in bringing about the first and is not changed by it, e.g., the key is an instrument in 'the key opened the door'; instrument and resource cannot be satisfied by the same ordered pair