Relation pm#agent__doer (situation [48..*],entity [49..*])
  supertype:  doer/object/result  who_relation
  subtype:  organizer (situation,causal_entity)
  subtype:  participant (situation,causal_entity)
  subtype:  seller__vendor___vender (situation -> goal_directed_agent)
  subtype:  customer__client___buyer__buyer___purchaser__purchaser___vendee (situation,goal_directed_agent)
  subtype:  responsible_agent__responsibleagent (situation,causal_entity)
  subtype:  agent (process,agentive_physical_object)  the 2nd argument is an active determinant, animate or inanimate, of the process