1<?xml version="1.0" standalone="no" ?> 2<!DOCTYPE test [ 3 <!ELEMENT test (extEnt)> 4 <!ELEMENT extEnt (sub2)> 5 <!ATTLIST extEnt attr CDATA #REQUIRED> 6 <!ELEMENT sub2 (#PCDATA)> 7 <!ENTITY extEnt SYSTEM "ent21.xml"> 8 ]> 9 10<test>&extEnt;</test>