<?xml  version="1.0"?>
<!-- validity constraint check for Production 56(Negative Test)-->
<!DOCTYPE test
 [
 <!ELEMENT test ANY>
 <!ELEMENT nametoken EMPTY>
 <!ATTLIST nametoken thistoken NMTOKEN #IMPLIED>
]>
<test>
<nametoken thistoken = "x : image"></nametoken>
In an attribute declaration, values of type NMTOKEN does not match the Nmtoken production
</test>