What is FoaF? FoaF is an acronym for Friend of a Friend, an experimental project and vocabulary for the Semantic Web. It is based on the idea of a machine-readable version of the current World Wide Web, with homepages, mailling lists, travel itineraries, calendars, address books and the likes. The FoaF vocabulary is most often used in RDF/XML files describing a person, usually augmented with othe