RDFをXHTMLに埋め込む規格のこと

Microformats, a simplified approach to semantically annotate data in web pages

Open Graph protocol, a way to use RDFa to integrate web pages into the Facebook social graph

Microdata - another approach at embedding semantics in HTML using additional attributes

eRDF, an alternative to RDFa (now obsolete)

GRDDL, a way to extract (annotated) data out of XHTML and XML documents and transform it into an RDF graph

Schema.org, search-engine supported schemas for structured data markup on web pages that can be expressed as RDFa