FOAF
RDF vocabulary
FOAF is an RDF vocabulary. The name FOAF is derived from the phrase friend of a friend :—
The name was chosen to reflect our concern with social networks and the Web, urban myths, trust and connections. Other uses of the name continue, notably in the documentation and investigation of Urban Legends (eg. see the alt.folklore.urban archive or snopes.com), and other FOAF stories. Our use of the name ‘FOAF’ for a Web vocabulary and document format is intended to complement, rather than replace, these prior uses. FOAF documents describe the characteristics and relationships amongst friends of friends, and their friends, and the stories they tell.
The initial aims of the FOAF vocabulary were twofold :—
- To aid in machine‐readable discovery of social networks (i.e. true “social networking”), and
- To provide rudimentary mechanisms for describing various agents for the purposes of document attribution.
Because it was developed over many years of real‐world use, FOAF lacks (and does not aspire to have) the rigour of a formal specification, instead positioning itself as a dictionary of terms.
The earliest FOAF vocabulary was offered as a “utility vocabulary” within the RDFWeb project, and its documentation was heavily driven by implementation experiments. In fact many of the spelling and stylistic inconsistencies in the names for FOAF terms came from the habit of testing things in real published RDF/XML files before documenting them in the central specification. The FOAF spec was as a result always framed in the role of a dictionary, documenting the terms used in published FOAF files. The vocabulary defined here was designed to serve a practical need: that of documenting work‐in‐progress vocabulary without confusing users and implying stability merely by some term appearing in the FOAF spec.
Nevertheless (or perhaps because of this), FOAF remains a popular and widespread choice for encoding basic metadata about persons and documents on the Web.
§ FOAF Autodiscovery
Because FOAF is often encoded in a machine‐readable format rather than a human‐readable webpage, enabling automatic discovery of FOAF metadata is a small challenge.
Servers of FOAF documents may not support content negotiation, and it is cumbersome for users to have to remember a separate URL for their FOAF document in addition to their homepage URL.
Fortunately, the HTML <link> mechanism can be used to point to an FOAF (or other RDF) metadata document from an ordinary HTML webpage :—
<link rel="meta" type="application/rdf+xml" title="FOAF" href="./foaf.rdf">
The rel="meta" is used to signify that the <link> provides metadata for the current document.
The type and href should change to match the location and filetype of the metadata document.