<a xmlns:x="urn:xxx" xmlns:y="urn:yyy" xmlns:z="urn:zzz">
    <b x:attr1="attval1">
        <x:c>
            <d z:attr2="attval2">
            </d>
        </x:c>
    </b>
    <y:e/>
    <z:f x:attr1="attrval1" z:attr2="attval2"/>
</a>