1  <!DOCTYPE doc [
 2  <!ELEMENT doc (a?, (b, c?, d?)?, (e | f | g)*, (h+ | i | j+))>
 3  <!ELEMENT a EMPTY>
 4  <!ELEMENT b EMPTY>
 5  <!ELEMENT c EMPTY>
 6  <!ELEMENT d EMPTY>
 7  <!ELEMENT e EMPTY>
 8  <!ELEMENT f EMPTY>
 9  <!ELEMENT g EMPTY>
10  <!ELEMENT h EMPTY>
11  <!ELEMENT i EMPTY>
12  <!ELEMENT j EMPTY>
13  ]>
14  <doc>
15  <i/>
16  </doc>