Relation pm#rdf_reification_relation__rdfreificationrelation (?,?)
  exclusion:  attributive_relation  purpose  has-author  owned-by  owner  owner_of  leader  seller  customer  generator  creator  spatial_origin  exploits  has_purpose  has_purpose_for_agent  measure  attribute  name  Date  value  support  example  syntax  has-magnitude
  supertype:  attributive_relation__attributiverelation  like pm#binary_relation, this type mostly exists to categorize what cannot be categorized elsewhere
  subtype:  predicate (statement -> binary_relation_type)  the property used in a statement when representing the statement in reified form
  subtype:  subject (statement -> ?)  resource that a statement is describing when representing the statement in reified form
  subtype:  object (? -> ?)  object of a statement when representing the statement in reified form