http://schema.org/Class
http://schema.org/SearchAction

SearchAction currently takes a query that might potentially be of type Class. We should change that to take a Thing instead.

This was a typo in one of the proposals we originally made, and it was meant to denote searching for "class of things" like "books". We have, however, moved on to a simpler approach where "class of things" are defined with "-input" statements and "templates of Things".