Relation pm#experiencer (pm#situation,pm#causal_entity)
  supertype:  pm#case_relation  pm#who_relation
  instance of:  pm#case_relation_type
  subtype:  sumo#experiencer (sumo#process,dl#agentive_physical_object)  e.g., Yojo is the experiencer of seeing in 'Yojo sees the fish'; unlike agent, this relation does not entail a causal relation between the arguments