<!-- Non-syntactic validity errors in default attributes only happen if the attribute is in fact defaulted. -->
<!DOCTYPE foo [
<!ELEMENT foo ANY>
<!ATTLIST foo id ID #IMPLIED>
<!ATTLIST foo ref IDREF "undef">
<!ATTLIST foo ent ENTITY "undef">
<!-- can't test NOTATION attribute, because if it's undeclared then we'll
     get an error for one of the enumerated values being undeclared. -->
<!ENTITY ent SYSTEM "foo" NDATA not>
<!NOTATION not SYSTEM "not">
]>
<foo id="g0034" ref="g0034" ent="ent"/>
