<?xml version="1.0" encoding="utf-8"?>
<!-- The following part is an internal DTD. 
     The DTD defines which structure is allowed
     in the XML content. -->
<!DOCTYPE people [
<!ELEMENT people (person)+ >
<!ELEMENT person (name , (profession)+  , (hobby)*)+ >
<!ELEMENT name   (first_name , (middle_initial)? , last_name) >
<!ELEMENT first_name (#PCDATA)>
<!ELEMENT last_name  (#PCDATA)>
<!ELEMENT profession (#PCDATA)>
<!ELEMENT middle_initial (#PCDATA)>
<!ELEMENT hobby      (#PCDATA)>
<!ATTLIST person
           born    NMTOKEN    #IMPLIED
           died    NMTOKEN    #IMPLIED>
]>
<!-- The following part is the element of this XML document -->
<!-- Example XML inspired from XML In A Nutshell -->
<people>
  <person born="1912" died="1954">
    <name>
      <first_name>Alan</first_name>
      <last_name>Turing</last_name>
    </name>
    <profession>computer scientist</profession>
    <profession>mathematician</profession>
    <profession>cryptographer</profession>
  </person>
  <person born="1918" died="1988">
    <name>
      <first_name>Richard</first_name>
      <middle_initial>P</middle_initial>
      <last_name>Feynman</last_name>
    </name>
    <profession>physicist</profession>
    <hobby>Playing the bongos</hobby>
  </person>
</people>