def base_metadata_url(alternate=None):
    """
    Return metadata URL.

    :param alternate: If the URL is for the simulator metadata. Default is False.
    :type alternate: str
    """
    baseurl = "http://downloads.blackberry.com/upr/developers/update/bbndk"
    tail = "{0}/{0}_metadata".format(alternate) if alternate is not None else "metadata"
    return "{0}/{1}".format(baseurl, tail)