<?xml version="1.0"?>
<!DOCTYPE root [
  <!ELEMENT root (a,b)>
  <!ELEMENT a EMPTY>
  <!ELEMENT b (#PCDATA|c)* >
  <!ELEMENT c ANY>

]>
<!--* root element have text content *-->
<root>
 root can't have text content
<a></a><b>
   <c></c> 
   content of b element
</b></root>