In my previous article on OpenID 2.0, I mentioned the new Attribute Exchange extension. To me this is one of the more interesting benefits of moving to OpenID 2.0, so it deserves a more in depth look. As mentioned previously, the extension is a way of transferring information about the user between the OpenID provider and relying party. Why use Attribute Exchange instead of FOAF or Microformats? Before deciding to use OpenID for information exchange, it is worth looking at whether it is necessary at all.