<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>

<!-- root ELEMENT   name   contains the sequence   first, middle?, last   elements -->
<!-- the question mark means zero or one   middle   elements -->

<!DOCTYPE name 
  [
  <!ELEMENT name (first, middle?, last) >
  <!ELEMENT first EMPTY >
  <!ELEMENT middle EMPTY >
 <!ELEMENT last EMPTY >
 ] >

<name>
  <first></first>
  <last></last>
</name>