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

<!-- root ELEMENT   name   contains the exactly sequence   first, middle, last   elements -->
<!-- use commas between the elements when you specify a sequence -->

<!DOCTYPE name 
  [
  <!ELEMENT name (first, (middle-name | middle-initial), last) >
  <!ELEMENT first EMPTY >
  <!ELEMENT middle-name EMPTY >
   <!ELEMENT middle-initial EMPTY >
 <!ELEMENT last EMPTY >
 ] >

<name>
  <first></first>
  <middle-initial></middle-initial>
  <last></last>
</name>