Function pm#sole_owner (? -> causal_entity)
  supertype:  owner (?,causal_entity)  this is not a function: 0..N owner allowed
     supertype:  attributive_relation__attributiverelation (*)  like pm#binary_relation, this type mostly exists to categorize what cannot be categorized elsewhere
        supertype:  relation_playing_a_special_role (*)  this type permits to categorize relations according to their roles ; this is a traditional but quite subjective 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:  who_relation__whorelation (*)
        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