element flatval {
    fs:item-sequence-to-node-sequence(
      let $s :=
        let $fs:v1 :=
          fs:promote-to-anystring(
            fs:convert-simple-operand(fn:data("seq.xml"), "")
          )
        return doc($fs:v1)
      return
        fs:distinct-docorder-or-atomic-sequence(
          let $fs:sequence :=
            fs:node-sequence(
              fs:distinct-docorder-or-atomic-sequence(
                let $fs:sequence :=
                  fs:node-sequence(
                    fs:distinct-docorder-or-atomic-sequence(
                      let $fs:sequence := fs:node-sequence($s),
                          $fs:last := fn:count($fs:sequence)
                      for $fs:dot at $fs:position in $fs:sequence
                      return child::seqval
                    )
                  ),
                    $fs:last := fn:count($fs:sequence)
                for $fs:dot at $fs:position in $fs:sequence
                return child::book
              )
            ),
              $fs:last := fn:count($fs:sequence)
          for $fs:dot at $fs:position in $fs:sequence
          return child::author
        )
    )
  }