Perspectives Workshop: Semantic Web Reﬂections and Future Directions, 29 June 2009
FOAF (Friend of a Friend)
the most used ontology in the history of the universe?
how the hell did that happen?
(Vrije Universiteit Amsterdam)
• FOAF today: a very quick overview
• Origins of FOAF (as the RDFWebRing)
• Happy Accidents (2000-2003)
• Success, Horrible Success! (2004-5)
• Recent & Future History (2008/9)
FOAF today: the basics
• the FOAF vocabulary, a few classes and
properties describing people, groups, etc.
• high visibility outside RDF/RDFS/OWL scene
• lots of data, and a few interesting apps
• for a side-project, it became very active
What’s so special?
Nothing huge - subtle shifts of emphasis:
Use of Web standards.
Use of Web identiﬁers.
Easy to extend.
People are interesting...
Web in 2000:
FOAF in 2000:
• hacker project of Libby Miller, Dan Brickley
and our friends from the RDF Interest
Group, W3C, RSS and XML tech scene.
• Used RDFS and DAML+OIL to document
our work, ... as a means not an end.
• Early themes: PGP, digital signature and
trust, crawlers, linking, photo annotation.
The basic idea behind FOAF is simple: the Web is all about making connections between
things. FOAF provides some basic machinery to help us tell the Web about the connections
between the things that matter to us.
Thousands of people already do this on the Web by describing themselves and their lives
on their home page. Using FOAF, you can help machines understand your home page, and FOAF is best explained with an example.
through doing so, learn about the relationships that connect people, places and things Consider a Web of inter-related home
described on the Web. FOAF uses W3C's RDF technology to integrate information from pages, each describing things of interest to
your home page with that of your friends, and the friends of your friends, and their friends.. a group of friends. Each new home page
that appears on the Web tells the world
something new, providing factoids and
Dan lives in Zetland road, Bristol, UK with Libby and gossip that make the Web a mine of
Craig. Dan's email address is email@example.com. Libby's disconnected snippets of information.
email address is firstname.lastname@example.org. Craig's is FOAF provides a way to make sense of all
email@example.com. Dan and Libby work for an this. Here's an example, a fragment from
organisation called "ILRT" whose website is at http:// the mostly-ﬁctional FOAF database. First
ilrt.org/. Craig works for "Netgates", an organisation we list some facts, then describe how the
whose website is at http://www.netgates.co.uk/. Craig's
FOAF system makes it possible to explore
wife Liz lives in Bristol with Kathleen. Kathleen and
the Web learning such things.
Liz also work at "Netgates". Damian lives in London.
Martin knows Craig, Damian, Dan and Libby quite well.
Martin lives in Bristol and has an email address of
This kind of information is the sort of thing typically found on Web home pages. The extract shown here indicates how short,
stylised factual sentences can be used to characterise a Web of relationships between people, places, organisations and
documents. In real life, this information would be most likely be distributed across variou s Web pages created by the individuals
listed. Very likely, their pages will link directly or indirectly to the home pages of countless other friends-of-friends-of-friends.
We want a better way of keeping track of the scattered fragments of data currently represented in the
We want to be able to ﬁnd documents in the Web based on their properties and inter-relationships...
We want to be able to ﬁnd information about people based on their publications, employment details,
group membership and declared interests.
We want to be able to share annotations, ratings, bookmarks and arbitrary useful data fragments using
some common infrastructure.
We want a Web search system that's more like a database and less like a lucky dip.
We need it to be be distributed, decentralised, and content-neutral.
RDFWeb/FOAF, if successful, should help the Web do the sorts of things that are currently the
proprietary offering of centralised services.
Original use cases
• We want to be able to ask the Web sensible questions and common kinds of
thing (documents, organisations, people) and get back sensible results:
• "Find me today's web page recommendations made by people who work
for Medical organisations"
• "Find me recent publications by people I've co-authored documents with"
• "Show me critiques of this web page, and the home pages of the author of
(see also EU DESIRE project, 1996-1999)
of Libby Miller, taken while at Oxford University"').
And it got big how?
• Libby Miller’s Java/Squish RDF query tools
• Edd Dumbill (of xml.com) wrote a nice
article on IBM DeveloperWorks.com
• Leigh Dodds created foaf-a-matic script, Ian
Davis (amongst other things) our logo
• RDF IG community built some early apps
• By 2003, Ecademy and TypePad exports
• In 2004, LiveJournal, Tribe, FOAFNet, ...
CoDepiction in 2002:
RDFWeb is intended to be both fun and technically challenging. We're trying to build a linked information system, RDFWeb,
as a way of connecting these two goals. In particular, we want RDF to present practical and interesting applications for the
Semantic Web, and explore ways of making them real. One of our favourite examples is photo metadata. This document tries
to explain why...
The (soon to be "Semantic") Web, if it is to reach its full potential, needs to become a lot more automatic. We hope that it will
be able to do things (offer us services) based on combining data and services scattered around the Web. It might, for
example, be able to ﬁnd the phone numbers or AOL screen names of all your friends and professional collaborators. Or show
you the photos, names and recent publications and shared bookmarks for everyone attending the next meeting in your
There are so many things the Web might usefully do in the future, that it is sometimes hard to see how we can get there from
here. W3C's RDF has been around since 1997, yet while it has been adopted in a number of applications (for example by
Mozilla, Open Directory, Adobe, RSS 1.0), people often ask why there is as yet no killer app for RDF. While we're not sure
that 'killer app' is the right way to think about the problem, it is true that there is relatively little RDF data 'out there in the
public Web', in the way that HTML is 'out there'.
The original idea behind RDFWeb was to experiment with making some cheap, simple RDF-based document formats that
were designed for deployment in the public Web. We began by asking 'What would it be like if machines could read my
homepage?', and by prototyping a simple vocabulary called FOAF ('Friend of a Friend'). The FOAF vocabulary provided a way
for RDF documents to talk about people and their characteristics. FOAF documents also make use of hypertext, providing
'seeAlso' links to other FOAF documents elsewhere in the Web. This simple convention makes it possible for RDF indexing
tools to explore an (RDF)Web of linked documents (hence the name of the project).
From foaf:knows to foaf:depiction...
Shortly after prototyping our early RDFWeb/FOAF tools, we ran into a design problem. The FOAF vocabulary initially tried to
deﬁne a number of basic relationships that could be used to describe connections between people in the Web. We
experimented with variations such as foaf:knows, foaf:friend and foaf:knowsWell. Eventually we decided that such a taxonomy
was neither appropriate nor deployable; we now simply use foaf:knows. Instead of trying to categorise subtle relationships
into broad classes, we took a different approach, focussing instead on other information about people. Documents they had
written (and who they were written with); Photos they'd taken (and who they'd taken them of). We expanded the early FOAF
support for image metadata by introducing the notion of a foaf:depiction. This relates something (eg. a person) to some
depiction of them (typically a digital image).
Crawling PGP-signed RDF:
exploiting PGP’s “web of trust”...
...and we got noticed
“The very important aspect of FOAF (at least here in Japan) is that FOAF is
getting to be the ﬁrst entry point to RDF/Semantic Web for ordinary people.
So many people say 'I ﬁrst time feel partly understand RDF' or 'This is my ﬁrst
experience to touch SW, wow!' in their blogs or diary pages.” --Kanzaki, June’03
you to create a FOAF ("Friend-of-A-Friend") description of
yourself. You can read more about FOAF in Edd Dumbill's
"XML Watch: Finding friends with XML and RDF" article, at
the FOAF homepage on RDFWeb, and also the FOAF
(translated into 12+ languages)
omogućava kreiranje FOAF ("Friend-of-A-Friend") opisa
neke osobe.Više o tome možete pročitati u članku Edda
Dumbilla XML Watch: Finding friends with XML and RDF"
koji možete pronaći na the FOAF homepage on RDFWeb,
kao i FOAF vocabulary description (opis FOAF rječnika).
hjælpe med at lave en FOAF-beskrivelse ("Friend-of-A-
Friend", "Ven-af-en-Ven") af dig selv. Du kan læse mere om
FOAF i Edd Dumbills artikel "XML Watch: Finding friends
with XML and RDF" ("Find venner med XML og RDF"), på
FOAF-hjemmesiden på RDFWeb samt i FOAF's tekniske
waarmee je een vriend-van-een-vriend beschrijving (FOAF
= "Friend-of-A-Friend") van jezelf kunt maken. Je kunt
meer lezen over FOAF in Edd Dumbill's "XML Watch:
Finding friends with XML and RDF" artikel, op de FOAF
homepage op RDFWeb, evenals de FOAF vocabulair
FOAF-a-matic FOAF ("Friend-of-A-Friend")
FOAF Edd Dumbill
"XML Watch: Finding friends with XML and RDF"
" RDFWeb FOAF FOAF
permet de créer une description FOAF ("Friend-of-A-
Friend", "Amis d'un ami") de vous même. Pour en savoir
plus sur FOAF vous pouvez lire l'article de Edd Dumbill,
"XML Watch: Finding friends with XML and RDF", la page
d'accueil de FOAF sur RDFWeb, et aussi the FOAF
vocabulary description ("Description du vocabulaire
permite crear un descripción FOAF ("Friend-of-A-Friend" o
Amigo-de-un-Amigo) de si mismo. Puede leer más (en
inglés) acerca de FOAF en el articulo de Edd Dumbill "XML
Watch: Finding friends with XML and RDF", en the FOAF
homepage on RDFWeb, y tambien the FOAF vocabulary
description. En castellano existe el documento "FOAF: el
proyecto 'Friend-of-a-friend'", de Leandro Mariano López.
dig skapa en FOAF ("Friend-of-A-Friend" eller "Vän-till-En-
Vän")-beskrivning av dig själv. Du kan läsa mer om FOAF i
Edd Dumbills artikel "XML Watch: Finding friends with
XML and RDF" på hemsidan för FOAF hos RDFWeb,
liksom beskrivningen av FOAF-vokabulären.
εφαρμογή, που επιτρέπει την δημιουργία
περιγραφών FOAF ("Friend-of-A-Friend", ελλ: "Φίλος
ενός φίλου") του εαυτού σας. Μπορείτε να
μάθετε περισσότερα για το FOAF στο άρθρο
"XML Watch: Finding friends with XML and RDF" του Edd
Dumbill, στην FOAF σελίδα του RDFWeb και στην
λεξικολογική περιγραφή του FOAF.
eine FOAF ("Friend-of-A-Friend" = Freund eines Freundes)
Beschreibung von dir erstellt. Mehr zu FOAF ﬁndest du in
Edd Dumbills Artikel "XML Watch: Finding friends with
XML and RDF" (Freunde ﬁnden mit XML und RDF), auf der
FOAF Homepage der RDFWeb Webseite oder auch in der
FOAF Vokabular Beschreibung.
permette di creare una descrizione di te stesso in formato
FOAF ("Friend-of-A-Friend", "Amico di un amico"). Puoi
avere maggiori informazioni su FOAF nell'articolo di Edd
Dumbill "XML Watch: Finding friends with XML and RDF",
sulla homepage di FOAF su RDFWeb, ed inﬁne nella FOAF
vocabulary description (descrizione del vocabolario FOAF).
Edd Dumbill XML
XML RDF RDFWeb FOAF
FOAF FOAF vocabulary
. FOAF FOAF
(Edd Dumbill) " XML
Watch: Finding friends with XML and RDF" FOAF
( the FOAF vocabulary description)
• Ecademy (Julian Bond)
• Morten’s FOAF Explorer service
• TypePad (hosted Movable Type blogs)
• 2002-2003: Edd’s article, foaf-a-matic and
early tools. Marc Canter’s FOAFnet...
• 2004 various exporters, Howard Dean’s
innovative Internet campaign, deanspace,
• 24x7 Internet Relay Chat (IRC) channels
• Discussions in blogs (daily searching)
• Informal style meetups and hacking
• Emphasis on making over specifying
• Internet/Web & XML culture
• or ... how our triplestores crumbled!
• all the early demos died
• took a few years for global services
• “me and near me” personal crawlers?
• some eg. plink.org closed due to privacy
concerns of users
How did LiveJournal get FOAF?
crschmidt: So, to the best of my knowledge, it went something like this:
crschmidt: 1. Roomate with neil. Neil is a deanspace hacker, I am an LJ hacker.
crschmidt: 2. Spend lots of time on LJ bug tracker. I seem to recall seeing ﬁxing LJ bugs as a personal vendetta. I started
hacking on LJ around Oct 2003, iirc (the bug tracker from that time is dead)
crschmidt: 3. There was an open bug on FOAF support in LJ, which I was working on before the lj-biz post. (It was
something like a 4 month process, so if it was deployed in Feb, it was dﬁnitely before that)
crschmidt: 4. Iterate iterate iterate over the bug/patch, waiting in some cases for LJ to improve in other ways for speed, etc.
crschmidt: 5. Finally get the work that I did deployed in Feb 2004
crschmidt: So, basically: Someone who could ﬁnd LJ's bugtracker thought it would be a good idea, and I had a tendancy to ﬁx
every bug I understood, that one ﬁt btter into my court than most because of the Deanspace connection in my
room, and that was my initial introduction to FOAF
crschmidt: I think that about sums it up, from what i remember
"A few people have asked "what's the point?" And to that I ask back, what is the point of RSS
and why did we bother implementing it here on LJ, even though people could just visit our
journals? RSS was implemented here because it's an open, machine-readable standard that has
been adopted by most of the blogging community to facilitate the sharing of information. One
of LiveJournal's core values is developing for the open source movement, and I think FOAF is
an exemplary project for which to extend this value. Of course there would be the option to
disable it. In fact, I think it should be opt-in, since it does provide personal information to the
-- Joe (bostonsteamer), 2004-01-04, ljbiz forum, LiveJournal
SWAD-Europe & DERI FOAF Workshop, Sept 2004
Bootstrapping the FOAF-Web: An Experiment in Social Network Mining Peter Mika
Descriptions of Social Relations Peter Mika, Aldo Gangemi
FOAF-Realm - control your friends' access to resources Sebastian Ryszard Kruk
Keyword Extraction from the Web for FOAF Metadata Junichiro Mori, Yutaka Matsuo, Mitsuru Ishizuka, Boi
Linking Semantically-Enabled Online Community Sites Andreas Harth, John G. Breslin, Ina O'Murchu, Stefan
Using RDF + FOAF to create a local business review and search network Chris Schmidt
Moleskiing: a Trust-aware Decentralized Recommender System Paolo Avesani, Paolo Massa, Roberto Tiella
A model of trust and anonymity in a content rating system for e-learning systems. Tom Croucher
Open Rating Systems R.V Guha
Ontological Consideration on Human Relationship Vocabulary for FOAF Yutaka Matsuo, Masahiro Hamasaki,
Junichiro Mori, Hideaki Takeda, Koiti Hasida
The People's Portal: Ontology Management on Community Portals Anna V. Zhdanova
Redeﬁning Web-of-Trust: reputation, recommendations, responsibility and trust among peers Viktor S. Grishchenko
rss4you: Web-Based Syndication Enhanced with Social Navigation Nicolas Nova, Roberto Ortelli
The Semantic Web as a Semantic Soup Harith Alani, Simon Cox, Hugh Glaser, Steve Harris
Technical and Privacy Challenges for Integrating FOAF into Existing Applications Joseph Smarr
The Challenges of FOAF Characterization John C. Paolillo and Elijah Wright
(remember CSS in 1996, gave us Ajax a decade later...)
• “it’s ok to publish FOAF, so long as nobody uses
it...” - users don’t expect to see their data
resurface elsewhere (yet...)
• Deanspace and plink.org (now ofﬂine)
• Tribe.net & explode.us
• CC-for-people? OAuth for privacy? XMPP
for desktop access? privacy policies? Let
Facebook and twitter and FriendFeed train
• NoTube project - FOAF and Social TV
• W3C context: SocialWeb group
• Web landscape: Linked Data everywhere
• Focus on ends not means: information
linking and making it useful for people...
• Help needed: stats, vocab patterns
• What’s the connection between LiveJournal
and DeanSpace? (room-mates)
• What’s the connection between Google
SGAPI and LiveJournal FOAF? (Bradﬁtz)
• Between Microformats, Portable Contacts
and FOAF? (an obsession with an open Web...)
“Does it matter if they
use our stuff?”
• re-thinking core values
• domain-neutral aspects
• “people description” aspects