String CRAWLER_DOCUMENT_HTML_CONTENT_XPATH = "crawler.document.html.content.xpath";

    /** The key of the configuration. e.g. //HTML/@lang */
    String CRAWLER_DOCUMENT_HTML_LANG_XPATH = "crawler.document.html.lang.xpath";

    /** The key of the configuration. e.g. //META[@name='description']/@content */
    String CRAWLER_DOCUMENT_HTML_DIGEST_XPATH = "crawler.document.html.digest.xpath";