<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE test [
	<!ELEMENT test ((id|idref)*)>
	<!ELEMENT id      EMPTY>
	<!ELEMENT idref   EMPTY>
	<!ATTLIST id
			id ID	#IMPLIED>
	<!ATTLIST idref
			idref CDATA #IMPLIED> <!-- we will use schematron to check IDREF -->
]>
<test>
	<id id="dummy"/> <!-- try commenting out this node and see what happens! -->
	<idref idref="dummy"/>
</test>
