Comments can be added within a DTD. DTD comments are normal XML comments.
<?xml version="1.0" standalone="yes"?> <!DOCTYPE rootelement [ <!-- rootelement is the root element --> <!ELEMENT rootelement (childelement1)> <!-- rootelement stores childelement1 data --> <!ELEMENT childelement1 (#PCDATA)> ]> <rootelement> <childelement1>Child element 1.</childelement1> </rootelement>