<?xml version="1.0"?>
<!DOCTYPE ideg [
<!ELEMENT ideg (dog , cat , catowner+)>
<!ELEMENT dog (#PCDATA)>
<!ELEMENT cat (#PCDATA)>
<!ELEMENT catowner (#PCDATA)>
<!ATTLIST dog id ID #REQUIRED>
<!ATTLIST cat id ID #REQUIRED>
<!ATTLIST catowner pet IDREF #REQUIRED>
]>
<ideg>
        <dog id="danny">Danny</dog>
        <cat id="bede">Bede</cat>
        <catowner>Harold</catowner>
        <catowner pet="poochi">Fumiaki</catowner>
        <catowner pet="danny">Jimmy</catowner>
        <catowner pet="bede">Rick</catowner>
</ideg>
