From FOAF

Contents 1 The Minimal FOAF Document 1.1 Document Skeleton 1.2 The Minimal Document 1.3 The Minimal Useful Document

[edit] The Minimal FOAF Document

This page describes the simplest possible, but arguably still useful FOAF document.

[edit] Document Skeleton

Here's the basic document skeleton for a FOAF document. Showing the root element of the RDF document and the relevant namespace declarations:

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:foaf="http://xmlns.com/foaf/0.1/">

    <!-- FOAF data goes here -->

</rdf:RDF>

Things to note:

• FOAF documents are RDF documents, and are therefore wrapped in the rdf:RDF element
• The FOAF namespace is http://xmlns.com/foaf/0.1/

The remaining examples in this page will assume that the elements are wrapped in this skeleton document.

[edit] The Minimal Document

The most minimal FOAF document is the following:

<foaf:Person/>

Which says "there is a person". Obviously thats not very useful as it doesn't say anything about the person or even assign them a unique identifier.

A useful extension would be to include the persons name:

<foaf:Person>
  <foaf:name>Dan Brickley</foaf:name>
</foaf:Person>

Which says "there is a person named Dan Brickley". (See NamingPeopleInFoaf for more information) This is marginally more useful, especially for human consumers of the data. However RDF is all about machine-processable descriptions of resources. RDF processors are much happier when there are unique identifiers for resources as it makes it easier to combine different peoples descriptions of that resource.

[edit] The Minimal Useful Document

Therefore our minimally useful FOAF document adds a unique identifier to our Person Resource. There are several ways to do this. The first involves adding the users email address like this:

<foaf:Person>
  <foaf:name>Dan Brickley</foaf:name>
  <foaf:mbox rdf:resource="mailto:danbri@rdfweb.org"/>
</foaf:Person>

FOAF declares that an email address ("mbox") is a unique, unambiguous identifier for a Person. For more discussion on this see MboxAsUniqueIdentifier. A FOAF application can then determine that if two people make statements about a Resource with the identifier "mailto:danbri@rdfweb.org" then they're actually talking about the same thing.

It's perfectly legal to include multiple foaf:mbox elements within a foaf:Person. This basically says that there are multiple unique identifiers for this person (one for each foaf:mbox), giving FOAF processors more chance of amalgamating data about that resource (see also Smushing).

Many people aren't comfortable with advertising their email address on the web; spam being a major concern. FOAF therefore defines another unique identifier for a person: foaf:mbox_sha1sum. This is the SHA1 sum of the persons email. SHA1 sum is, for all practical applications, a way to generate a unique code from a text string. You can generate a SHA1 hash of your email address using either Bill Kearney's online Hash Generator (Link Broken) or Morten Frederikson's sha1ify.

Here's how to introduce it into your FOAF document:

<foaf:Person>
  <foaf:name>Dan Brickley</foaf:name>
  <foaf:mbox_sha1sum>748934f32135cfcf6f8c06e253c53442721e15e7</foaf:mbox_sha1sum>
</foaf:Person>

Which says "there is a Person called Dan Brickley who has an email address whose sha1 hash is...".

FOAF processors can then go about Smushing people together using their foaf:mbox_sha1sum instead of their foaf:mbox.