<http://schema.org/description>
"In 2009, site speed became a ranking factor and Google launched several tools for webmasters to track their site speed.  One of those tools was launched in December 2009 and it was found within Google"^^<http://www.w3.org/2001/XMLSchema#string>
<https://www.seroundtable.com/google-site-performance-lag-13138.html>