Why Use a DTD?
n DTDs allow software translation filters to be
developed with confidence that the markup used
during document preparation conformed to a
known specification, and was applied consistently.
n Example DTD:
<!ELEMENT warning (para*, image?)>
<!ELEMENT para (#PCDATA | emph | keyword)*>
<!ELEMENT image EMPTY>
<!ELEMENT emph (#PCDATA)>
<!ELEMENT keyword (#PCDATA)>