<?xml version="1.0"?> <!DOCTYPE zoo [ <!ATTLIST species id ID #REQUIRED> ]> <zoo> <class> <name>Reptiles</name> <species id="Chamaeleo-chamaelon" name="Chameleon" specimens="2"/> </class> <class> <name>Birds</name> <species id="Dromaius-novaehollandiae" name="Emu" specimens="12"/> <species id="Tyto-alba" name="Barn Owl" specimens="4"/> <species id="Corvus-corax" name="Raven" specimens="0"/> <location>Aviary</location> </class> </zoo>