PUBLIC MARKS with tags sémantique & rdfa

The Open Graph protocol enables you to integrate your web pages into the social graph. It is currently designed for web pages representing profiles of real-world things — things like movies, sports teams, celebrities, and restaurants. Once your pages become objects in the graph, users can establish connections to your pages as they do with Facebook Pages. Based on the structured data you provide via the Open Graph protocol, your pages show up richly across Facebook: in user profiles, within search results and in News Feed.

Common Tag is an open tagging format developed to make content more connected, discoverable and engaging. Unlike free-text tags, Common Tags are references to unique, well-defined concepts, complete with metadata and their own URLs. With Common Tag, site owners can more easily create topic hubs, cross-promote their content, and enrich their pages with free data, images and widgets.

tutorial on RDFa