/** The key of the configuration. e.g. //LINK[@rel='canonical'][1]/@href */
    String CRAWLER_DOCUMENT_HTML_CANONICAL_XPATH = "crawler.document.html.canonical.xpath";

    /** The key of the configuration. e.g. noscript,script,style,header,footer,aside,nav,a[rel=nofollow] */
    String CRAWLER_DOCUMENT_HTML_PRUNED_TAGS = "crawler.document.html.pruned.tags";