[foaf-dev] proposal for foaf:openid property

Dan Brickley danbri at danbri.org
Sun Jun 17 00:38:26 BST 2007

Draft in progress. Anyone object to this going into the spec?

Property: foaf:openid
openid - An OpenID for an Agent.
Status: 	unstable
OWL Type: 	An InverseFunctionalProperty (uniquely identifying property)
Domain: 	foaf:Agent
Range: 	foaf:Document

A foaf:openid is a property of a foaf:Agent that associates it with a 
document that can be used as an indirect identifier in the manner of the 
OpenID "Identity URL". As the OpenID 1.1 specification notes, OpenID 
itself"does not provide any mechanism to exchange profile information, 
though Consumers of an Identity can learn more about an End User from 
any public, semantically interesting documents linked thereunder (FOAF, 
RSS, Atom, vCARD, etc.)". In this way, FOAF and OpenID complement each 
other; neither provides a stand-alone approach to online "trust", but 
combined they can address interesting parts of this larger problem space.

The foaf:openid property is "inverse functional", meaning that anything 
that is the foaf:openid of something, is the foaf:openid of no more than 
one thing. FOAF is agnostic as to whether there are (according to the 
relevant OpenID specifications) OpenID URIs that are equally associated 
with multiple Agents. FOAF offers sub-classes of Agent, ie. 
foaf:Organization and foaf:Group, that allow for such scenarios to be 
consistent with the notion that any foaf:openid is the foaf:openid of 
just one foaf:Agent.

FOAF does not mandate any particular URI scheme for use as foaf:openid 
values. The OpenID 1.1 specification includes a delegation model that is 
often used to allow a weblog or homepage document to also serve in 
OpenID authentication via "link rel" HTML markup. This deployment model 
provides a convenient connection to FOAF, since a similar technique is 
used for FOAF autodiscovery in HTML. A single document can, for example, 
serve both as a homepage and an OpenID identity URL.

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