If we change that prefix binding later on, we'll get different names:

<o:order xmlns:o="urn:publicid:IDN+cde.berkeley.edu:example:order:en">
  <o:from>me</o:from>
  <o:to>you</o:to>
  <o:items xmlns:o="urn:publicid:IDN+cde.berkeley.edu:example:order:items:en">
    <o:item>A clue</o:item>
    <o:item>A better clue!</o:item>
  </o:items>
  <o:memo>
    <p>I need this order now!</p>
  </o:memo>
</o:order>