<?xml  version="1.0"?>
<!-- validity constraint check for Production 56(Negative Test)-->
<!DOCTYPE test
 [
 <!ELEMENT test ANY>
 <!ELEMENT id1 EMPTY>
 <!ELEMENT id2 EMPTY>
 <!ELEMENT idrefs EMPTY>
 <!ATTLIST id1 UniqueName ID #REQUIRED>
 <!ATTLIST id2 UName ID #IMPLIED>
 <!ATTLIST idrefs reference IDREFS #IMPLIED>
 ]>
<test>
<id1 UniqueName = "BC456"></id1>
<id2 UName = "AC567"></id2>
<idrefs reference = "EF456 DE355"></idrefs>
Negative test for validity constraint of IDREFS.
In an attribute decl, values of type IDREFS match the name production
but IDREFS value do not match the values assigned to one or more ID attributes
somewhere in the XML document
</test>