<?xml version="1.0"?>
<!DOCTYPE root [
<!ENTITY % deftest "<!ELEMENT test (#PCDATA) >">
<!ENTITY % defmiddle "<!ELEMENT middle (test) >">
<!ENTITY % defroot "<!ELEMENT root (middle) >">
<!ELEMENT root (middle)>
<!ELEMENT middle (test)>
<!ELEMENT test (#PCDATA)>
]>
<root><middle><test>sample</test></middle></root>