XML DTD Sample
<?xml version="1.0"?>
 <!DOCTYPE PUBLICATION
[<!ELEMENT PUBLICATION(TITLE,AUTHOR+,ABSTRACT*)>
 <!ELEMENT AUTHOR (FIRSTNAME, LASTNAME,
                  (UNIVERSITY | COMPANY)?)>
 <!ATTLIST AUTHOR role (author|techwriter) "author">
 <!ELEMENT FIRSTNAME (#PCDATA)>
 <!ELEMENT LASTNAME (#PCDATA)>
 <!ELEMENT UNIVERSITY (#PCDATA)>
 <!ELEMENT COMPANY (#PCDATA)>
 <!ELEMENT ABSTRACT (#PCDATA)>
 ]>
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