XML File Example
<!DOCTYPE DWELLING SYSTEM "dwelling.dtd" [
<!ENTITY person "X">
<!ENTITY dog "D">
<!ENTITY cat "C">
<!ELEMENT ROOM (FURNITURE? & ITEM)+ >
<!ELEMENT FURNITURE (ITEM+)>
<!ELEMENT ITEM (#PCDATA)>]>
<DWELLING>
<ROOM Name="The Kitchen">
<FURNITURE>Table</FURNITURE >
&dog; &person;
<ITEM>Dish</ITEM>
</ROOM>
<ROOM Name="Marvin's Room">
&cat;
<FURNITURE">
Chair
<ITEM>Coin</ITEM>
</FURNITURE >
</ROOM>
</DWELLING>