<!ELEMENT x12simple (loop)*>

<!ELEMENT loop (loop | seg)*>
<!ATTLIST loop id CDATA #REQUIRED>

<!ELEMENT seg (ele | comp)*>
<!ATTLIST seg id CDATA #REQUIRED>

<!ELEMENT comp (subele)*>
<!ATTLIST comp id CDATA #REQUIRED>

<!ELEMENT ele (#PCDATA)>
<!ATTLIST ele id CDATA #REQUIRED>

<!ELEMENT subele (#PCDATA)>
<!ATTLIST subele id CDATA #REQUIRED>