At the Identity Commons we're building a persistent global and/or local identity infrastructure using the OASIS standard for Extensible Resource Identifiers (XRI). Coupled with XRI Data Interchange (XDI) and the powerful link contract mechanism, we are building a system for personal profile control and interchange that rivals FOAF (though once again I have to make the disclaimer that I am no FOAF expert).

Given the tremendous popularity of FOAF, we'll have to "embrace and extend" FOAF with XDI. The biggest problem with FOAF is that profile sharing is done on a FOAF-file level of granularity, so I'd actually have to have multiple FOAF files if I wanted to share different information with different entities. Storing all the FOAF info in a database and dynamically creating a specialized (WRT the requester) FOAF file is one way to get around this limitation. But even then, the requester now has a copy of the file unencumbered by (e.g.) XDI link contracts that could prevent him/her from passing it on or otherwise using it in manners originally unintended.


Uh, hi. Please keep me posted

Uh, hi. Please keep me posted with progress on the "embrace and extend" operation. One quick point re FOAF: if you understand FOAF as a dictionary of terms that can be used in RDF/XML documents and messages, rather than as a static file format, it may seem closer to your concerns. While a common deployment pattern for FOAF is to publish .rdf files via a public HTTP server, FOAF can be used in any context where there is value in exchanging descriptions that use FOAF terminology. This includes protocols, P2P, PGP-signed data, etc.

I have had a look around the XDI stuff and can't really see where it is heading. The white paper outlines some value over RDF's data model; I'd be interested to see tools, services, data etc that make those distinctions more observable to a casual reader who hasn't followed XDI closely.

the best page to watch to keep an occasional eye on this?

Hi Dan - Great to make the

Hi Dan - Great to make the connection! I was thinking that the terminology "embrace and extend" - as popularized by a certain evil empire - might catch a few eyes. ;-)

I am a fan or RDF and believe it to be an excellent tool, first coming across it in my work with P3P some years ago. As FOAF is based upon RDF - and as it is widely used today - perhaps FOAF embedded within XDI might be the best initial protocol for extending the reach of social networks. The XDI white paper (at the link you refer to) discusses the concept of "link contracts" which enable active identification and data interchange control - features that might well be used to enhance FOAF's ability to describe relationships to (with?) data.

Your question of where to go to find out more about XDI comes at an opportune time - we're just *starting* to be able to answer that. The best place to start might be the XRI/XDI public wiki at - be sure to check out the XdiUseCases which are now being filled in. In particular, there's a SocialNetworks use case that currently is FOAF-based, but I expect that it will soon include more about the use of link contracts for fine-grained datum authorization.