imperative_document =
  (#choice [
    (#exact-list [canon_document_name canon_title])
    (#exact-list [canon_document_name canon_title canon_id])
    (#exact-list [canon_document_name canon_title canon_id canon_type])
    (#exact-list [canon_document_name canon_title canon_type canon_id])
    (#exact-list [canon_document_name canon_title canon_type])
  ])
