Semantic annotation and retrieval: Web of hypertext - RDFa and microformats

For the Semantic Web to succeed in a major, public setting, it needs to leverage the existing Web. Two major technologies have emerged over the last few years to bridge the vast, existing ‘‘clickable’’ Web and the new Semantic Web: Microformats and RDFa. Both allow authors to embed extra information within (X)HTML to mark up the structure, not just the visual presentation, of the information they publish. In this chapter, both approaches are explained, exploring their strengths and weaknesses, providing example applications, and touching on future considerations. 5.1 Scientific and Technical Overview