One other interesting feature of OpenID is the ability for the OpenID provider to supply (upon the user's consent) typical user registration data such as name, e-mail, and date of birth, if the OpenID-enabled website requests it. This functionality is called Attribute Exchange (AX). The following diagram illustrates how a request for attribute exchange makes it into the OpenID request:
The AX attribute values (if supplied by the provider) are returned along with the rest of the OpenID response, and inserted into the
OpenIDAuthenticationToken as a
AX attributes can be arbitrarily defined by OpenID ...