if links.select {|link| link.rel=="alternate" and link.type == "application/vnd.iso.19139+xml"}.size == 0
          self[:links] << Hashie::Mash.new({ "href" => "#{api}/dataset/#{id}.iso",
            "rel" => "alternate", "title" => "ISO 19139 XML", "type" => "application/vnd.iso.19139+xml"})