Schema.org Hosted Extension: meta

Schema.org is a set of extensible schemas that enables webmasters to embed structured data on their web pages for use by search engines and other applications. 
For more details, see the homepage. 

The meta extension contains terms primarily designed to support the implementation of the Schema.org vocabulary itself.  It includes terms such as Class, Property, domainIncludes and supersededBy.  They are not currently advocated for widespread use across the web.