Fragment identifiers for <source> and <target>

Hi TC folks,

We've been working on an XLIFF 2.0 object model and have a question about fragment identifiers.

<xliff xmlns="urn:oasis:names:tc:xliff:document:2.0" version="2.0" srcLang="en" trgLang="fr">
 <file id="f1">
  <unit id="u1">
   <segment id="s1">
    <source>Hello World</source>
    <target>Bonjour le Monde</target>
   </segment>
  </unit>
 </file>
</xliff>

#f=f1/u=u1/s1 refers to the element <segment id="s1"> of the element <unit id="u1">, but is there a mechanism to select <source> or <target> of <segment id="s1"> individually without inline markup?

Thanks,
Ryan