This document discusses data formats on the social web. It describes vocabularies used to define terms for exchanging and integrating data between applications. In particular, it describes FOAF (Friend of a Friend), an ontology used for publishing personal profile data and social relationships as linked RDF documents. FOAF allows integrating factual information about people with other human-oriented content on the web. The document also briefly mentions challenges of cleaning and transforming messy social web data into consistent formats.