A More Complex DTD
<!ELEMENT SONG (TITLE, PHOTO?, COMPOSER+, PRODUCER*,
PUBLISHER*, LENGTH?, YEAR?, ARTIST+)>
<!ATTLIST SONG xmlns CDATA #REQUIRED
xmlns:xlink CDATA #REQUIRED>
<!ELEMENT TITLE (#PCDATA)>
<!ELEMENT PHOTO EMPTY>
<!ATTLIST PHOTO xlink:type CDATA #FIXED "simple"
xlink:href CDATA #REQUIRED
xlink:show CDATA #IMPLIED
ALT CDATA #REQUIRED
WIDTH CDATA #REQUIRED
HEIGHT CDATA #REQUIRED
>
<!ELEMENT COMPOSER (#PCDATA)>
<!ELEMENT PRODUCER (#PCDATA)>
<!ELEMENT PUBLISHER (#PCDATA)>
<!ATTLIST PUBLISHER xlink:type CDATA #IMPLIED
xlink:href CDATA #IMPLIED
>
<!ELEMENT LENGTH (#PCDATA)>
<!-- This should be a four digit year like "1999",
not a two-digit year like "99" -->
<!ELEMENT YEAR (#PCDATA)>
<!ELEMENT ARTIST (#PCDATA)>