RDFa

[2] RDFa was first proposed by Mark Birbeck in the form of a W3C note entitled XHTML and RDF,[3] which was then presented to the Semantic Web Interest Group[4] at the W3C's 2004 Technical Plenary.

Indeed, one of the earliest documents bearing the RDF/A Syntax name has the sub-title A collection of attributes for layering RDF on XML languages.

[8] The document was written by Mark Birbeck and Steven Pemberton, and was made available for discussion on October 11, 2004.

Although described as not representing an intended direction in terms of a formal markup language from the W3C, limited use of the XHTML+RDFa 1.0 DTD did subsequently appear on the public Web.

[10] October 2007 saw the first public Working Draft of a document entitled RDFa in XHTML: Syntax and Processing.

[11] This superseded and expanded upon the April draft; it contained rules for creating an RDFa parser, as well as guidelines for organizations wishing to make practical use of the technology.

While it is not a complete solution for advanced data markup tasks, it does work for most day-to-day needs and can be learned by most Web authors in a day.

RDFa Lite consists of five attributes: vocab, typeof, property, resource, and prefix.

Simplified approaches to semantically annotate information items in webpages were greatly encouraged by the HTML+RDFa (released in 2008) and microformats (since ~2005) standards.

Moreover, RDFa allows the passages and words within a text to be associated with semantic markup: The following is an example of a complete XHTML+RDFa 1.0 document.

Further into the paragraph, a span element containing an about attribute defines the book as another resource to specify metadata about.

Here are the same triples when the above document is automatically converted to RDF/XML: The above example can be expressed without XML namespaces in HTML5: Note how the prefix foaf is still used without declaration.