RDFa (Resource Description Framework in Attributes) is a technique that allows to express structured data in markup languages. It provides a set of attributes to augment the visual information on the Web with machine-readable hints.
RDFa is a W3C Recommendation for embedding rdf data in markup languages (like HTML, XHTML, SVG, etc.).
Example
The following XHTML snippet (from the RDFa 1.1 Primer linked below), the document has "The Trouble with Bob" as a value of the property dc:terms as well as the content of an h2 element. It also has a dc:created value of 2011-09-10. Because the additional information is specified by attributes on the elements, it does not affect the display of the XHTML document.
<html>
<head>…</head>
<body>
…
<h2 property="http://purl.org/dc/terms/title">The Trouble with Bob</h2>
<p>Date: <span property="http://purl.org/dc/terms/created">2011-09-10</span></p>
…
</body>
What questions should use this tag?
Questions about adding RDFa annotations to a document, or extracting RDF data from an RDFa document should use the rdfa tag.
References
The W3C has published several documents regarding RDFa, including an introductory primer as well as the normative recommendations:
