DTD Example
<!ELEMENT NAME (FIRST,MIDDLE,LAST)> <!ELEMENT FIRST (#PCDATA)> <!ELEMENT MIDDLE (#PCDATA)> <!ELEMENT LAST (#PCDATA)> <!ELEMENT AGENCY (#PCDATA)> <!ELEMENT PHONE (AREA_CODE,PREFIX,NUMBER)> <!ELEMENT AREA_CODE(#PCDATA)>
<!ELEMENT PREFIX(#PCDATA)>
<!ELEMENT NUMBER(#PCDATA)>