* desired, and use YYYY-MM-DD.
     *
     * Note that this tag is separate from the If-Modified-Since (304) header
     * the server can return, and search engines may use the information from
     * both sources differently.
     */
    private String lastmod;

    /**
     * How frequently the page is likely to change. This value provides general
     * information to search engines and may not correlate exactly to how often