<!DOCTYPE exa [
	
<!ELEMENT exa (a|b)*>
<!ELEMENT a EMPTY>
<!ELEMENT b ANY>

<!ATTLIST a x (yes|no)         "yes"
            y (yes|perhaps|no) "no">
<!ATTLIST a x NMTOKEN "yes">
]>

<exa>
<a></a>
<b/>
</exa>

