RDFa

RDFa (Resource Description Framework in Attributes) is a W3C specification that lets authors embed RDF triples in markup languages such as HTML5, XHTML and arbitrary XML by adding a small set of attributes to existing elements. RDFa 1.0 became a W3C Recommendation in October 2008, originally targeting XHTML, and was substantially revised as RDFa 1.1 in June 2012 to support HTML5 and general XML. A simplified profile, RDFa Lite 1.1, was released alongside the full specification. RDFa Lite uses only five attributes — vocab, typeof, property, resource and prefix — which together express a subject-predicate-object triple on any element. The vocab attribute names a default vocabulary, typeof declares the class of the current subject, property names the predicate and supplies a literal value from the element's text, and resource or about identify the object resource. Because the attributes coexist with normal HTML, RDFa lets a single document serve both human readers and semantic web consumers. RDFa is one of the three encodings supported by <a href="/knowledge/Schema.org" class="link" style="color: #D4A843;" title="Direct link to chunk">Schema.org Structured Data</a>, alongside <a href="/knowledge/Microdata" class="link" style="color: #D4A843;" title="Direct link to chunk">Microdata (HTML)</a> and <a href="/knowledge/json-ld" class="link" style="color: #D4A843;" title="Direct link to chunk">JSON-LD</a>. It is used by publishers who already maintain templates with semantic class names — notably Drupal, which has shipped RDFa output by default — and remains valid for search-engine rich results. In aggregate web crawls, however, RDFa now trails JSON-LD by a wide margin because authors find the latter easier to template and to validate.