XML in a Nutshell, 3rd Edition

DTDs for Record-Like Documents

DTDs for record-like documents are very straightforward. They make heavy use of sequences, occasional use of choices, and almost no use of mixed content. Example 3-6 shows such a DTD. Since this is a small example, and since it’s easier to understand when both the document and the DTD are on the same page, we’ve made this an internal DTD included in the document. However, it would be easy to extract it and store it in a separate file.

Example 3-6. A DTD describing people

<?xml version="1.0"?>
<!DOCTYPE person  [
  <!ELEMENT person (name+, profession*)>
  <!ELEMENT name EMPTY>
  <!ATTLIST name first CDATA #REQUIRED
                 last  CDATA #REQUIRED>
  <!-- The first and last attributes are required to be present
       but they may be empty. For example,
       <name first="Cher" last=""> -->
  <!ELEMENT profession EMPTY>
  <!ATTLIST profession value CDATA #REQUIRED>
]>
<person>
  <name first="Alan" last="Turing"/>
  <profession value="computer scientist"/>
  <profession value="mathematician"/>
  <profession value="cryptographer"/>
</person>

The DTD here is contained completely inside the internal DTD subset. First a person ELEMENT declaration states that each person must have one or more name children, and zero or more profession children, in that order. This allows for the possibility that a person changes his name or uses aliases. It assumes that each person has at least one name but may not have a profession.

This declaration also requires that all name elements precede all profession elements. ...