Direct how to handle the identifier element.

def identifier_director(**kwargs):
    """Direct how to handle the identifier element."""
    ark = kwargs.get('ark', None)
    qualifier = kwargs.get('qualifier', None)
    content = kwargs.get('content', '')

    # See if the ark and domain name were given.
    if ark:
        content = 'http://digital.library.unt.edu/%s' % ark
    elif qualifier:
        content = '%s: %s' % (qualifier, content)
    return ETD_MSIdentifier(content=content)