docs: def identifier_director(**kwargs):
      """Direct how to handle the identifier element."""
      ark = kwargs.get('ark', None)
      domain_name = kwargs.get('domain_name', None)
      # Set default scheme if it is None or is not supplied.
      scheme = kwargs.get('scheme') or 'http'
      qualifier = kwargs.get('qualifier', None)
      content = kwargs.get('content', '')
      # See if the ark and domain name were given.
      if ark and qualifier == 'ark':
          content = 'ark: %s' % ark
      if domain_name and ark and qualifier == 'permalink':
          # Create the permalink URL.
          if not domain_name.endswith('/'):
              domain_name += '/'
          permalink_url = '%s://%s%s' % (scheme, domain_name, ark)
          # Make sure it has a trailing slash.
          if not permalink_url.endswith('/'):
              permalink_url += '/'
          content = permalink_url
      else:
          if qualifier:
              content = '%s: %s' % (string.lower(qualifier), content)
      return DCIdentifier(content=content)