<http://schema.org/description>
"This is a topic we covered in the past, but I had the opportunity to remind you all, that Google prefers you use a server status code of 503, when your site is going down for maintenance.  Googler, Jo"^^<http://www.w3.org/2001/XMLSchema#string>
<https://www.seroundtable.com/archives/018873.html>