XFN™ (XHTML Friends Network) is a simple way to represent human relationships using hyperlinks. In recent years, blogs and blogrolls have become the fastest growing area of the Web. XFN enables web authors to indicate their relationship(s) to the people in their blogrolls simply by adding a 'rel' attribute to their <a href> tags, e.g.:

<a href="http://jeff.example.org" rel="friend met">... 

See http://gmpg.org/xfn/

The great advantage over move complicated formats like FOAF is that it integrates directly into (X)HTML and the code for generating it is very simple to write. Moreover it can be used for identity consolidation, basically you can have in your primary identity (say, you blog or your CS page) all the links to your identities in other services (such as flickr, youtube, ... and possibly in other hospitality networks as well). It is a simple and effective way to tie all your identities together.

XFN is just one of many microformats. See this presentations about microformats or more presentations. Shall we integrate microformats in the HTML produced by CS site in more places? Where?

Another microformat we might like to implement on CS is hCard.

Implemented in CSv277. But the HTML doesn't validate yet so a lot of tools can't handle it.

Free Software for visualizing the XFN network

• xfngraph, check Java web start

See also Visualization of Networks.