Relation pm#instrument (situation,entity)
  subtype:  instrument  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
  supertype:  object/result (situation,?)
     supertype:  doer/object/result (situation,?)
        supertype:  doer/object/result/place (situation,?)
           supertype:  case_relation__thematic_relation (situation,*)
              supertype:  relation_from_situation (situation,*)
                 supertype:  relation_from/to_thing_of_common_kind (*)  this type permits to categorize relations according to their signatures and hence offers (i) a concise way to set essential exclusion relations, and (ii) a systematic and easy-to-follow categorization
                    >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
     supertype:  what_relation (*)
        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 
           >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
  supertype:  how_relation__howrelation (*)
     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