Document Type Definition (DTD)
<!ELEMENT SONG (TITLE, PHOTO?, COMPOSER+, PRODUCER*,
PUBLISHER*, LENGTH?, YEAR?, ARTIST+)>
<!ELEMENT TITLE (#PCDATA)>
<!ELEMENT COMPOSER (#PCDATA)>
<!ELEMENT PRODUCER (#PCDATA)>
<!ELEMENT PUBLISHER (#PCDATA)>
<!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)>
<!ELEMENT PHOTO EMPTY>
<!ATTLIST PHOTO xlink:type (simple) #FIXED "simple"
xlink:show (onLoad) #FIXED "onLoad"
xlink:href CDATA #REQUIRED
ALT CDATA #REQUIRED
WIDTH NMTOKEN #REQUIRED
HEIGHT NMTOKEN #REQUIRED
>
<!ATTLIST PUBLISHER xlink:type (simple) #FIXED "simple"
xlink:href CDATA #REQUIRED
>
<!ATTLIST SONG xmlns CDATA #FIXED "http://metalab.unc.edu/xml/namespace/song"
xmlns:xlink CDATA #FIXED "http://www.w3.org/1999/xlink"
>