Enumerations

• List of all allowed values from which one must be chosen

• A choice containing value elements

The publisher must be one of the oligopoly that controls 90% of U.S. music (Warner-Elektra-Atlantic, Universal Music Group, Sony Music Entertainment, Inc., Capitol Records, Inc., BMG Music)

<?xml version="1.0"?>
<element name="SONG" xmlns="http://relaxng.org/ns/structure/1.0">
  <element name="TITLE">
    <text/>
  </element>
  <oneOrMore>
    <element name="COMPOSER">
      <text/>
    </element>
  </oneOrMore>
  <zeroOrMore>
    <element name="PRODUCER">
      <text/>
    </element>
  </zeroOrMore>
  <optional>
    <element name="PUBLISHER">
    <choice>
      <value>Warner-Elektra-Atlantic</value>
      <value>Universal Music Group</value>
      <value>Sony Music Entertainment, Inc.</value>
      <value>Capitol Records, Inc.</value>
      <value>BMG Music</value>
    </choice>
  </element>
  </optional>
  <optional>
    <element name="LENGTH">
      <text/>
    </element>
  </optional>
  <optional>
    <element name="YEAR">
      <text/>
    </element>
  </optional>
  <oneOrMore>
    <element name="ARTIST">
      <text/>
    </element>
  </oneOrMore>
</element>

element SONG {
  element TITLE    { text },
  element COMPOSER { text }+,
  element PRODUCER { text }*,
  element PUBLISHER {
    "Warner-Elektra-Atlantic"
    | "Universal Music Group"
    | "Sony Music Entertainment, Inc."
    | "Capitol Records, Inc."
    | "BMG Music"
  }?,
  element LENGTH { text }?,
  element YEAR   { text }?,
  element ARTIST { text }+
}