<http://schema.org/description>
"JohnMu from Google posted in a Google Webmaster Help thread that Google typically crawls a site's robots.txt file on a daily basis.  This is the first time (at least that I can remember) I have seen a"^^<http://www.w3.org/2001/XMLSchema#string>
<https://www.seroundtable.com/archives/020695.html>